Here are some tutorials. Some of them are prepared by myself (projects prepared by me may require AVR Project IDE).
AVR General Tutorials
AVR Programming Introduction - Hack a Day, there are several parts.
AVR-GCC Tutorial - Scienceprog.com, a collection of tutorials about using AVRs
AVR tutorials - AVR Freaks, a collection of tutorials about using AVRs on the AVR Freaks forums
Tutorials on SparkFun, the "Beginning Embedded Electronics" section focuses on AVR microcontrollers.
Turn USnooBie into an USBasp, make your own USB in-circuit programmer for Atmel AVR controllers with an USnooBie
See a massive list of V-USB projects, check this out for examples and ideas.
Stealth USB CapLocker, neat little prank using a tiny PCB that inserts right into the USB port.
Haunted USB Cable, same as the Stealth USB CapLocker, but hidden inside a USB cable.