If you want a good game similiar to Peggle then get Rockchinko. Very good Peggle clone with some added stuff like use of the accelerometer.
I was about to mention that game too. Problem is, I played it before peggle and didn't like it too much, it was ver meh. Nevertheless, you might like it, it's all about tastes and preferences.
Need to try Pipe Mania, it is on sale for $.99 this weekend Really has grabbed me like Peggle did and though the menus are ugly, there are a LOT of unlockables and game modes. Also the core gameplay never seems to get old as the pipes are randomized, with neat little twists thrown in every couple of levels.
Dynoquest is actually very good since I've been playing the pre-release version. I don't know what the ETA is, but I know it was submitted a while ago.
I think GadgetGuru wants REALLY good games rather than similar type. I'd recommend Rolando 2. That game while a platformer, is amazing on the iPhone. It might be a bit of leap from StoneLoops and Peggle, but it's absolutely worth it.
Pegs in Space Rockchinko Bounce Trap Tilt If you are kinda hardcore you might like all the available Pachinko titles in the store... Try out any lite version if you don't know what Pachinko is.