Over on the Make blog, there's a great list of a bunch of Arduino kits, books, and add-ons.
The Arduino open-source microcontroller platform can be programmed and equipped to perform a nearly endless list of functions. It's likely the best all-around centerpiece to a modern electronics project. But one of the tasks Arduino is best used for is straight-up fun - the open design means there's an Arduino board suitable for almost any project, and a wealth of add-on "shields" extends its abilities with ease.Make's gift guide to Arduino
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects