I really like this one and use it a lot, Photo Transfer. It transfers photos and videos directly from your iPad to your computer via a Wi-Fi connection or Bluetooth and from your computer to your iPad. I use it with a Wi-Fi connection. It’s simple and works as advertised. It’s just really direct. It simply copies the the image or video files from one device to another. No muss, no fuss. 2.99 and worth every penny.
I also use the Kindle emulator app for books. I still generally read actual books made out of paper but it’s nice to have the option to instantly download a Kindle version from Amazon, if it’s available, and read it on the iPad. I also like having a little library on my iPad for when I travel. Application is free, books, generally not.
And I still like my streaming Netflix. If you have a Netflix account, or ever watch anything on Hula, those apps are handy. Something else I generally like having for when I travel. App free, Netlix and Hulu Plus account, not free.
TED Talks has an app if you like those; nothing but TED talks, all the time. Free app.
And I don’t know if you are a birdwatcher, but I am a very, very amateur backyard and occasional birdwatcher and I like my iPad Audubon field guide. It’s not an adequate substitute for a decent library of bird books and CDs but I really like the “multi-medianess” of it. I like having visual identification information, a bit of info on habitat and behavior and the audio of the bird calls and songs all in one reference, one nice little package. Audubon Field Guides generally 19.99 and under.
Also, Pandora and Spotify are good music apps, I think, and I use them a lot. Both can be free or paid depending what features you want and would use.
Those are a few that I like and find useful. Apps are kind of a personal thing. It really depends on you and what you like and want to use your iPad for.