There's a small but interesting set of drawing apps available on the iPhone. While it may well be up for debate, Autodesk Sketchbook Mobile is arguably the standout software of the bunch.
Why? One reason - a robust feature set. With a wide selection of drawing tools, great file management, layers, detailed zoom and multiple levels of "undo," it's easily the most desktop-like of all drawing apps we've seen.
Sketchbook Mobile opens to a blank canvas where you can begin waxing your creative fingers right away. More importantly, it doesn't make drawing on a mobile device any more difficult. If you've got skills, you can draw conveniently on the iPhone - guaranteed. Like to turn out pieces that look like you went through an entire shelf of instruments? Not a problem with a full-bodied selection of 25 different palettes, including an option to make your own custom brushes.
A lone tap on the screen gives you quick access to the menu, where you can access all the various tools - including brush selection, layers, color wheel and a mirroring tool (literally replicate what you drew on the other side of the sheet). Used to drawing in layers? Not a problem as the app supports up to three on old iPhones and six on the iPhone 3GS. Made a mistake? You'll love the ten layers of undo available, which is more than what I've seen some older PC drawing programs do. The zoom feature, by the way, is incredibly helpful, allowing you to blow up the sketch to up to 2,500 percent.
The app builds its own gallery, where you can perform basic file management, apart from viewing items one by one. Images can be imported from a camera roll on the fly, either as the base image or as a new layer. Oh yeah, you can export your drawings to a PSD file (all layering is retained) for later editing on Photoshop too.
Priced at only $2.99, Sketchbook Mobile is easily the best value among the App Store's drawing apps. More than that, though, I sincerely believe it's the best of the lot as well.