If you have an iPad2, take a look at this from inCase: Lounge Case. I got it when I got my mom her iPad and she really likes it. It's got little beads in it so it'll mold to your legs/lap. Very nice, actually.
On the inCase web site, they've got it listed at $59.99 (USD), but I've seen it elsewhere for $49.99. Just do some Googling...
Oh, and if you go to the Best Buy website, some guy has done a video review of it, so you can "see it in action." TBH, I'm kind of jealous that my mom has it and that I can't get it for the classic iPad (I wrote the company, they have zero plans to develop one for the iPad1).
I'll be honest with you - I want one real bad. I am so jealous that my mom, with her iPad2, has a nice holder and I don't.
So, I'm probably going to buy one, cut the iPad2 curved bits out of it and then glue it to the back of an iPad1 back cover.
Words simply cannot describe how nicely this thing works in your lap ... and my frustration when the company told me they weren't making one for the iPad1.