Systems I manage at home and at work:

• Slackware 10.1, 10.2, 11.0, and 12.1 on Intel Pentium III and 4
• OpenBSD 4.3 on Intel Pentium III
• Slax and Knoppix Live CDs on Intel platforms mentioned above
• OpenBSD 4.2 on Pentium 166 (my gateway to the outer world)
• DEC VT-420 saved from garbage collection (a terminal, not a 'real' computer)
• Solaris 8 and 9 on Sun Fire V880, V480, 280R, E-250 and Ultra-10
• i5/OS V5R3 on IBM AS/400, and eServer i5
• ...some other commercial OSs on Intel platforms