Hmm... if you only look at that site, you're missing out on a lot.
Throw in a dose of http://epiacenter.com
- that'll give you enough non-project related stuff.
Of course, the VIA C3 is the most common CPU on Mini-ITX.
However, the Pentium M, Pentium 4 (S478, LGA775, and LGA775 dual-core (that's coming soon)), Pentium 3, Transmeta Efficieon, and the AMD Geode (including the NX, which is a ULV Athlon XP-M) are all represented on Mini-ITX. Granted, all but the Pentium 4 boards are VERY expensive...