Ooh, if you're thinking of a Kindling Fire, wait until the next Colo(u)r Nook comes out. Rumor is that it's being announced Nov 7. Nook Colo(u)r has removable microSD so you can install a different operating system. With luck, B&N is smart enough to continue this practice.
My latest technology-related purchase was an Amtrak (USA passenger rail) ticket to go to the ARM TechCon and see a RaspPi alpha first-hand and chat with Eben. I also got a free STM32F4-Discovery board. The thing I really like about the STM Discovery boards is that you can easily disable their ST-Link, hook up your own JTAG, and not have to use anyone else's software (well, except for the FTDI USB driver). I don't know if you can do this anywhere as easily with an NXP Mbed or LPXpresso The STM32F407VG on the board is Cortex-M4 with (if I'm reading the product spec correctly) 1MB Flash, 192K RAM, Enet MAC, two USBs, ADCs, DACs, and a slew of serial interfaces.