Atmel AVR Microcontroller Primer
Programming and Interfacing (Synthesis Lectures on Digital Circuits and Systems) by Steven F. Barrett, Daniel Pack and Mitchell Thornton (Dec 15, 2007)
Bascom-AVR Programming
This easy to understand manual is both a useful learning tool and a good reference manual to keep handy on your workbench. Starting out with the basics of microcontroller programming, it proceeds to cover intermediate and advanced topics of Atmel's AVR Microcontroller family. The programming aspect of the book focuses on the widely popular Bascom-AVR compiler, which is a very user-friendly Basic compiler/IDE developed in the Netherlands.
C Programming for Microcontrollers
Featuring ATMEL's AVR Butterfly and the free WinAVR Compiler by Joe Pardue (Mar 1, 2005)
Embedded C Programming and the Atmel AVR
by Richard H. Barnett, Sarah Cox and Larry O'Cull (Jun 5, 2006
Practical AVR Microcontrollers
Games, Gadgets, and Home Automation with the Microcontroller Used in the Arduino (Technology in Action) by Alan Trevennor (Oct 10, 2012)
Programming and Customizing the AVR Microcontroller
Dhananjay V. Gadre (Sep 18, 2000)
Read more: Programming and Customizing the AVR Microcontroller
tinyAVR Microcontroller Projects for the Evil Genius
Dhananjay Gadre and Nehul Malhotra (Jan 18, 2011)
Read more: tinyAVR Microcontroller Projects for the Evil Genius