Here are the ones I've been using the most so far (got my iPad 2 last Tuesday)
Dropbox for getting files on the device easily.
Goodreader for reading and marking up PDFs
Atomic Web Browser--I love tabbed browsing and the private browsing feature
Evernote for organzing my notes from meetings etc. ( I take them in the Notes app) and synching them to all my PCs.
Kindle App for e-books (I have a Kindle and still mainly read on it) so prefer this to iBooks or the others as it's were my books are).
Netflix
DirecTV if you're a member. Fast way to check the guide, set up recordings if you have a DVR etc.
News Apps: NY Times (going to $20 a month--but Top News section will remain free), USA Today, Politico, NPR, BBC, CNN, Zite, Pulse, The Hill
Sports Apps: ESPN ScoreCenter, NBA Courtside Game Time, March Madness
Weather.com app
Games: Plants vs. Zombies, Angry Birds, Words With Friends, whatever free solitaire app you like best etc.
Skype--iPhone app only, but still looks good. Essential for me as I don't have any friends/family on facetime currently as like me they're all PC people.
Marvel and Comixology for comics
Zinio for magazines
Pandora for streaming music
OpenTable for making restaurant reservations if you live in a city
Epicurious--great free cookbook
Backgrounds--huge collection of wallpapers
Dictionary.com
Dropbox for getting files on the device easily.
Goodreader for reading and marking up PDFs
Atomic Web Browser--I love tabbed browsing and the private browsing feature
Evernote for organzing my notes from meetings etc. ( I take them in the Notes app) and synching them to all my PCs.
Kindle App for e-books (I have a Kindle and still mainly read on it) so prefer this to iBooks or the others as it's were my books are).
Netflix
DirecTV if you're a member. Fast way to check the guide, set up recordings if you have a DVR etc.
News Apps: NY Times (going to $20 a month--but Top News section will remain free), USA Today, Politico, NPR, BBC, CNN, Zite, Pulse, The Hill
Sports Apps: ESPN ScoreCenter, NBA Courtside Game Time, March Madness
Weather.com app
Games: Plants vs. Zombies, Angry Birds, Words With Friends, whatever free solitaire app you like best etc.
Skype--iPhone app only, but still looks good. Essential for me as I don't have any friends/family on facetime currently as like me they're all PC people.
Marvel and Comixology for comics
Zinio for magazines
Pandora for streaming music
OpenTable for making restaurant reservations if you live in a city
Epicurious--great free cookbook
Backgrounds--huge collection of wallpapers
Dictionary.com