@DBAlex
Yes, sir. Linux on Dreamcast. It's been a while since I've tinkered with it, but I think the SH Linux kernel has everything you need to run it on Dreamcast. There used to be quite a few how-to documents out there, but Dreamcast development has all but disappeared over the last few years. My own setup includes an early Dreamcast model (don't know the revision), a broadband adapter (BBA), a Sega-branded US keyboard, and a Sega-branded US mouse (you can also use a gamepad). You can do most everything you need to do with either the BBA or a serial cable ("coder's cable"). I have both and used the serial cable for debug output.
PM your setup (I think the Dreamcast model number might be relevant), and I'll see if I can point you in the right direction. I may even be able to whip an ISO image or at least some how-to instructions for you. The most difficult part (well, not really) is setting up a cross compiler. Dan Kegel's Crosstool scripts are mighty useful:
http://www.kegel.com/crosstool/. Dan's also a very helpful guy, although I don't think he's using the SH stuff personally. We sorted out some Cygwin-related issues a few years ago. On Windows, Cygwin, coLinux, and Microsoft's Services for UNIX (or the bits that are now bundled with Windows) all make excellent development environments. I use Cygwin for tools and Visual Studio as my IDE.
Trev