TouchDraw for Android is a powerful, yet easy to use, vector 2D drawing and diagramming application for Android Tablets and Phones.  It has many of the features of desktop applications wrapped up in a mobile package.  Best of all, it's only a fraction of the price of a desktop application.

TouchDraw for Android is fully compatible with TouchDraw for iPad and TouchDraw for Mac and files can be freely exchanged between all three versions.  TouchDraw differs from a paint program in that objects are always managed independently of the drawing they're in.  You can move a figure around, change its shape, change its color, group it, without affecting other shapes that are around it.