I recently bought this great kit:
$40 for an ARM Cortex M3 microcontroller plus a color LCD touchscreen!
There are a couple of variations of this board on eBay, I bought mine from here: http://stores.ebay.com/PowerMCU-Electronics
If you ask them nicely they will send you the newer revision of this board, which has two mini USB ports instead of the USB B and DB-9 port.
*STM32F103RBT6 mcu: LQFP64-pin, 72MHz (96MIPS), 128k flash, 20kRAM, 16Bit A/D, PWM, CAN, USB device, USARTs
*Detachable, color 320x240 LCD with touchscreen, the screen module also has an SD card slot
*The board is about 85mmx65mmx25mm with the screen
*You don't need a programmer to start playing with it, as all STM32 chips come with a software bootloader (read-only so it's impossible to mess it up), allowing for firmware uploading through UART, using a free "flash loader demonstrator" tool from ST.
*Comes with a CD with documentation/schematics and code samples for using the screen (most of the documentation is in Chinese, though
*Can be used with the Yagarto open-source ARM toolchain, works on Windows and Linux
*ChibiOS/RT open-source operating system works on it almost out of the box, giving you easy multitasking and lots of other features
*Setting up the compiler environment is not exactly easy (if you want to use free tools)
*32-bit means more power, but also more problems
*Harder to find tutorials for STM32 online (compared to AVR for example)