1. Tweet a file : Tweetafile brings an important email functionality to the simple world of Twitter – attachments. Through Tweetafile, Twitter users can send any files (images, PDFs, Docs, videos… whatever) to all of their followers or via direct message to individuals.
2. Remember The Milk : If you use Remember The Milk to manage your tasks, you can do so via twitter using this app. Add Remember The Milk as your twitter friend and simply DM to add or interact with your tasks.
3. Twittonary : If you are new to twitter, some of the words twitter users use can be quite confusing. Get help from a twitter dictionary and learn the “twitter lingo.”
4. Twonvert : 140 character limitations at times can really hold you back. This app converts your text into SMS shorthand language and allows you to say more with less characters.
5. Twist : Allows you to see “hot trends” on twitter. You can also use the search box to see what people are saying about a particular thing and how much buzz it is creating.
6. WhosTalkin : Although this app isn’t specifically for twitter, it is a very useful twitter tool. It allows you to search conversations that you are interested in. This helps you interact with like minded people or the whatever subjects interest you at that point in time.
7. TweetWhatYouSpend : Manage your spending online using twitter. Create an account and use Twitter’s “DM” feature to send tweets. You can export a spending journal later as an Excel or CSV file.
8. TwitterJobSearch : This service allows you to find job postings on twitter. If you are looking for a “web design” gig, simply enter web design to see what jobs are available related to web design.
9. IsTwitterDown? : If you are a heavy twitter user this service might be quite useful. It allows you to find out if twitter is down for everyone else or just for you. The page displays a simple answer “Yes” or “No.”
10. Twiddeo : Upload videos to Twiddeo from your camera phone while on the go. The service then generates a link and posts it to twitter for your friends and followers to see.
11. TwitterCal : This tool connects your twitter account to your Google calendar. You can add events to Google calendar from twitter by sending direct messages to gcal.
12. TwitterFeed : Twitterfeed helps you send your Blog RSS feed or atom to twitter and also lets you track the number of clicks your feeds are generating.
13. PollDaddy : Create polls and post it directly on twitter. This can be extremely valuable when you are researching a subject or need user feedback.
14. LinkBunch : Due to character constraints, it can be quite hard to send more than one link in a tweet. If you need to send multiple links in one tweet (example : a post that has part1,2,3…), this service can be useful. It collects all links and gives you one shortened link that you can post on twitter.
15. Tweetdeck : One of the best desktop twitter apps out there. Tweetdeck helps you sort your friends and followers in groups and also helps you manage replies, DMs and search results.

1. Evernote

You’ll never forget your thoughts and tasks if you use Evernote. This powerful application stores all of your information in your personal Evernote account and can be retrieved on the Web, on your desktop, and on your phone. To get your stuff into Evernote, create new notes using the desktop, Web, and mobile versions of Evernote; take a snapshot using your camera phone or webcam, and the app will recognize the text in the image; clip Webpages and screenshots; drag and drop content into the desktop clients for Mac and Windows; e-mail notes to your account; scan receipts, tags, and the like; and record audio wherever you are and listen to it later.

2. Remember The Milk

Whether your preferred method of receiving reminders is through e-mail, SMS, or instant message, Remember The Milk offers them all. This to-do list Web service lets you create as many lists as you like, share them with others, and tag them. Say you create a grocery shopping list and need to know if there’s a coffee shop near the grocer on your way home; Remember The Milk will locate where the store is and what’s around it by interacting with Google Maps. Besides using the Web site to send your reminders, you can also use the service through Google Calendar, Twitter, Google Gears, MilkSync for BlackBerry, and download it to the Apple iPhone for free.

3. Backpackit.com

Web-based organizational service that’s both straightforward and intuitive, letting you download calendars and share documents online. We like to think of the service as an online loose-leaf notebook that you can use whenever you please, inputting medical records, travel plans, school itineraries, social gatherings, and so on onto every page. When you sign up, you’ll create a username and password as well as a unique Backpackit.com URL for easy access to your Backpack pages. You can add as many notes and lists as you want to your page, and Backpack’s messaging service lets you schedule e-mail or SMS reminders to be sent out at a specific time or at a Backpack preset time.

4. Doomi

Doomi is a simple-to-use desktop app that takes little effort to set up. All you do is add a task in the form field and press Enter. Click on the clock icon on the ride side to remind you of the task at a designated time. When you’ve finished a task, mark the checkbox next to it. Before you install Doomi, you’ll need to download Adobe AIR (Adobe Integrated Runtime): It’s a runtime engine for Windows, Mac, and Linux that supports rich Internet applications and allows an application to run without using a Web browser. That means you’ll be able to use Doomi offline, without running your Web browser.

5. Google Calendar

Organize your events and collaborate with others using Google Calendar. The application looks like a calendar, so all you do is click on which days you’d like to add your event or task. Then fill in the start time, end time, location, and description of your event, and set your desired notification setting, whether it’s by e-mail, text message, or a pop-up message on your computer. You can even send an invitation to your event, or information about your event, to others. Access Google Calendar on your mobile phone by pointing your browser to mobile.google.com/calendar.

6. ReminderFeed

Most reminder services alert you via e-mail and text message; but ReminderFeed delivers your messages right to your RSS reader. Just fill in the online form—including start date, end date, and description—and ReminderFeed will give you a feed URL that you can add to your favorite RSS reader. You’ll receive your reminder at the same time each day, which comes in handy for timely tasks such as picking up the kids from daycare or remembering a dinner date. Best of all, you don’t have to create an account, so just dive right in.

7. Toodledo

Never have to remember anything again with Toodledo. This online tool offers a “hotlist” where all of your tasks are permanently stored with due dates. Toodledo offers inline editing so that you can add, edit, and complete tasks without making the page reload. There are folders for organizing your tasks, a calendar for a visual presentation of your tasks due, and so much more. You can get Toodledo on your mobile phone, in your e-mail, on your calendar, in your RSS reader, via IM, and integrated directly into your Web browser. You can even print out a foldable booklet of all your tasks. Toodledo is now available for the iPhone/iPod touch.

8. Cozi

Designed specifically for families, Cozi is a free service that provides you and your family with everything you need to get organized. With the Family Calendar, all of your appointments can be color-coded by family member. You can build customizable lists to remember your grocery list, shopping list, chores, and more. Get appointment reminders by text and e-mail. Or send a quick message to your family from your family home page. Sign in to Cozi from your computer, phone (at m.cozi.com), or call Cozi toll-free to get your grocery list.

9. Jott

Not near a computer to create your to-do lists? Then you’ll want to use Jott for capturing thoughts, creating lists, and setting reminders—all by phone. Call 1-866-JOTT-123 to dictate your message, then say whether you want that message to be delivered via e-mail or SMS. Jott will capture your voice, turn it into text, and send it off. You can set Jott to remind you 15 minutes before a task needs to be started. Your notes are always available online at Jott.com in the Jott Express desktop tool, too. Download Jott to your Apple iPhone; it’s free for Jott subscribers and replicates most of the functionality in Jott’s call-in service.

10. Nozbe

Targeted at both individuals and businesses, Nozbe is a project-management and time-tracking application for those with a lot of stuff to do and no time to keep track of it all. Organize your tasks and notes into projects, ‘star’ any task that needs to be done next, schedule appointments using the built-in calendar, and manage your Nozbe account on your iPhone, iGoogle, or Netvibes homepage, or even on Apple Dashboard.