AVPlayerHD for watching movies and TV shows. Download any video format on your computer and then push to the iPad via iTunes or if the file is small enough just use wifi. You can create folders in AVPlayer as well
Zite and Flipboard for personalized magazine and news feeds
Week Cal HD was the ultimate calendar tool, but Apple took it away I think
Atomic Web Browser was the best, but again, Apple took the full version away. Terra is a good web browser and far better than Safari.
Quickpix is by far the best photo app. Nothing like being able to take 20 shots a second for sport mode.
My Photos is a good app to create folders and place pictures into said folders.
Snapseed is great for photo editing.
Dropbox and Dropcopy are great for moving files to the iPad wirelessly, like PDFs, mp3's, photos and the like.
Splashtop is great for remote controlling your Mac. Allows you to use Flash on your iPad, "virtually".
System Info free - a great utility app to tell you everything about your iPad, battery, network, etc