GroupMe: We fell in love with GroupMe at CES, but at that point the app itself was sort of secondary to the whole experience. No more! The free app got a big update, making the default messaging option free "push" messages that get piped in over your data connection (for chat that's both quicker and cheaper than SMS) as well as bringing FourSquare integration and more. Free.
Evernote: Evernote, many a note-junkie's powertool for keeping things in order, just reworked its iOS app from top to bottom. Which is good! Evernote's always been so packed with features that their smaller-device interfaces tended to come off a bit overwhelming. The highlights of the new design: a new home screen with an information-dense snippet view; a new split-view note screen which allows for multiple attachments to a single note; and easy browsing by notebook or tag. Free.
Fight Night Champion: Fight as boxing legends past and present in the newest Fight Night installation from EA, which has truly impressive graphics and squeezes an incredible amount of gesture control onto a 3.5" interface (swipe this way to throw an uppercut; swipe this way to throw a haymaker, etc.). I'm not a violent guy by nature, but even I can appreciate the multiplayer mode, which lets you womp on your friends via Bluetooth or local Wi-Fi. $5.
MTV Music Meter: Would you believe me if I told you MTV might actually help you find some new music to listen to? Not by playing videos on their TV station, of course, but with their free new Music Meter app for iOS and Android. Basically you can browse a chart of new trending artists (or hunt around the database yourself) and peep photos, bios, and 30 second audio clips courtesy of Rhapsody. Free.
Ditto: Ditto is an iPhone app reminiscent of Foursquare, but instead of announcing a check-in now, the app lets you tell your friends what you plan to do-then they get to counsel you how you should do it. The buttons for various activities let you choose "Eat out", "Work", "At home", etc. Afterwards, Ditto friends can give you suggestions to flesh out the details of your plan, like where you should eat in the area. Free.
Yobongo: Currently serving NYC, San Francisco, and Austin, TX (where else), you just fire up the app and see who else in your area happens to be chatting. The user base is pretty small right now, so our "New York" group included like all of New York, New Jersey, and Brooklyn, but presumably once more people join that radius will get smaller and smaller and chats will get more and more geographically intimate. Free.
TurboTax SnapTax: It's not for everyone: You have to have an income of 80k or less, have no dependents or real estate ownership, and get your income only from W-2s or unemployment. But if you meet those requirements (I do!), TurboTax SnapTax for Android and iOS has got to be the most painless way to deal with those inscrutable tax forms. Just use your smartphone to take a photo of your W-2, answer some (far less convoluted) questions supplied by the app, and then file them electronically. Free.