Mérida
One of the most spread out sites (70 square miles and counting!) around two lakes which is very unusual in the Yucatan. Lots of walking between the principal buildings with piles of rubble off to all sides, but the tallest Mayan pyramid in Northern Yucatan and the largest number recorded (41000,000,000,000,000 ish).
Uxmal
In danger of becoming another Maya World but we probably caught it just in time. The best Mayan architecture of the tour and a nice ambience (no monkeys but plenty of big iguanas).
and coming soon to this site... the Final Mexican Beer List, lots of piccies and credits for the nice Internet places we've used.