TUAW's Daily App: Darkroom Pro
And newer versions (after a short buggy delay right around iPhone OS 3.0) have added even more functionality, including a fullscreen shutter mode (no toolbar, just press anywhere on the screen to shoot a picture) and a timer mode as well. They've also added an online photo album into the app using StepCase's official service (which I've never used), but you can also just funnel pictures into your normal camera album if you'd rather upload them somewhere else. The latest update, released just this week, lets you tag your photos by place, so you can browse them later according to the location they were taken at.
Darkroom Pro is definitely worth the 99 cent price if you do any regular photography with your iPhone at all. There's also a free version available, and while the functionality on that one is limited, it still does have a steady mode included, so you can at least jump in and give that a try.
I've been a fan of the Darkroom app for the iPhone almost since the beginning, only because it contained a bit of functionality I think...