A while back, we bought a Sun Ultra 5 workstation with a winning bid of about $20.00 or so. It has a 360 MHz SPARC processor, 128 Meg of RAM, and an eight gigabyte harddrive.
And then for getting Debian to run on it
Depending on your particular machine, you might be able to install either Solaris or Linux. We first attempted to install Solaris 10 on the Ultra 5. It seemed to install okay, but when we rebooted, we received all kinds of error messages about how either our hardware was broken, or we were missing drivers. So, rather than trying to mess around with that, we downloaded the SPARC version of Debian Linux, and installed that.