Dropbox. Sync your files across all of your devices (home computer, work computer, laptop, smartphone). Share folders with others, like you would with a shared drive. Let others upload to or download files from your Dropbox. (See this blog post for more info.)
CloudConvert. You have a file in one format, but you want it in a different format. This service will do the transformation for you.
Delicious. (or other social bookmarking service). Save your bookmarks where you can access them from all of your devices, including your smartphone. Share some or all of your bookmarks. Tag them so they’re easy to find. (See this blog post for more info.) [A note of caution: The future of Delicious is unknown as of January 2011. Yahoo bought Delicious in 2004, but then never did much with it. Yahoo has let their Delicious staff go. Now the question is whether Yahoo will sell off Delicious, if they'll even find a buyer. I've used other bookmarking services, but Delicious is the one I continue to prefer. It does exactly what I want without layering on a lot of other functions that clutter things up. If you'd like try a different service, take a look at Diigo, my second choice.]
Followup.cc. I’ve tried many different task management tools. They all require me to go someplace to get my task list. Followup.cc puts my tasks where I live, in my email and in my calendar. (See this blog post.)
Share your desktop
LastPass. Remember one password and have access to all of your passwords – even on your smartphone. LastPass will generate random passwords for you – and remember them for you. You can even share a password with someone else, say, the person you share a bank account with.
IFTTT. Automatically have your gmail attachments saved to Dropbox. Tweet Feedly articles you’ve tagged. Text new appointments to Google calendar. Making these kinds of automated connections is the power of today’s internet. And you know what? It’s ridiculously easy to do. Read more here.
Cel.ly. Text all of your students at once or just texts individuals without getting their phone numbers or revealing yours. Send out a multiple choice question, and Cel.ly will tally the results for you. Read more here.