mini2440 is a good example of board that is cheap, has complete open source stacks (I'm the maintainer of the kernel and bootloader for it) and has a choice of several screen sizes. And it's been out for years.
Or you can use even cheaper devices too (I bought some at £6!), like the Parrot df3120 which I hacked a couple of years back, and gives you an ARM9, a 3.5" screen and a bluetooth transceiver to play with:
https://sites.google.com/site/repurposelinux/df3120
There are many, many others, from the sheevaplug range of "plug computers" to the beagleboard (which BTW even if old has a CPU way better than what's on the Raspberi) or the myriad of others, not even including the ones that are "repurposed"
If you want to learn to program and not just want another gadget to put on a shelf, you can program in your web browser, there are many websites that allow you to play with various languages, like Cloud9 for example. And if you /really/ want to learn program some hardware, you can very well do it on a 8 bits MCU like the AVR (arduino) -- ***er all they are a lot closer to the old 8 bits machines of the 80s.
As a professional embedded linux developer, I really find the "revolutionize the teaching of programming" argument of rasperi nothing short of disgusting, really. The fact it's amplified by the press of course (they got coverage in the Daily Wail for beeeeep sake!) but still, they are milking it.