[steaktartaar_]

Z80 micros are a lot of fun. I was looking for a kit last year and ended up building this one:

http://cpuville.com/Z80_kit.html

Getting it to work and writing simple programs is really satisfying and totally worth the burns from learning how to solder.

[XtalJ]

Yes, the programming is the fun part so if you don't want to design a new computer from ground up, a kit or a complete computer is to recommend :-)