If you'd like something with more of an Electrical Engineering bent, nerdkits are pretty good, and they use the same chips. They still have a bootloader, but ot

If you'd like something with more of an Electrical Engineering bent, nerdkits are pretty good, and they use the same chips. They still have a bootloader, but other than that it seems to be raw C, bitbanging, interrupts, all that sort of thing :)