Bamboo Paper

If you're nostalgic for good old pen and paper or a sketchbook, Bamboo Paper does a good job of recreating the feeling on a screen. Bamboo Paper is a very well-designed app that's aesthetically pleasing to use but also helps you organize notes and drawings.

You can choose from a number of different notebook styles or themes, with various paper types, colors and textures. You can add pictures and photos to your notes, and export to online storage sites such as DropBox and Evernote and share via Facebook, Twitter and Tumblr.

But there's no way to either import PDFs and annotate them or export notes and documents that you've saved as a PDF to send to someone else.