The new Facebook app helps you keep connected and has a very nice design. Upload pics, comment on your posts and even use Facebook chat as an Instant Messenger.
Dropbox helps you keep track of your files. For example: you put your work files into Dropbox and then print up your files to bring to work. Woops! You forgot your printed up files at home, luckily you go to work and download the files from Dropbox.
Skype enables you to make either free or really cheap calls to other Skype accounts.The design an layout is pretty simple but lacks notifications.
Dragon Dictation is literally your personal secretary. If you're to hurried to type a long text message just record your voice and it will turn it into text. Even tho it can't spell words like "supercalafragalisticexpialadoshus" it can turn simple words into text.
Paper Toss is a very good game to play while you're bored (at work,in the car,etc.) Try to throw the crunched up ball of paper into the garbage bin, with the difficulty of a fan changing the trajectory of the paper.
If you have any more apps that I should have included, please comment. I will have a vote soon to decide the #1 app.