Tim Dalton, at Theology Degrees On-Line, has posted a helpful entry titled "25 Incredible iPad Apps Every Theology Student Should Have." Take a look! I commend it.
Update (9/14/11): I should have included an item that I have found useful with my iPad2. Until someone comes out with an app that enables one to type in Greek characters, you may find typegreek.com useful. For instructions on its use look here. The tool generates Unicode Greek font.
Update (9/16/11): I discovered, today, that iPad 2 is capable of typing in polytonic Greek. So, now I use it instead of typegreek.com. Woo hoo!