IBM is giving away Cloudscape, an Open-Source Java RDBMS. It’s platform independend (if you can run Java, you can run Cloudscape) and it has a small footprint (about 2Mbyte) so it can be used for smart-devices (PDAs, cellphones).
If you live in the US or in Canada, you can even participate in their challenge where you can win an Apple iPod.
Click on the title to go to the download page and the challenge page.
If I find the time, I’ll try to find out if it’s worth your time. I have a trial version of Borland JBuilder 2005 somewhere on a DVD, so perhaps that’s a good combo to try out. JB2005 and Cloudscape.