Time Tree of Life
a database of taxonomic divergence times, primarily from DNA sequencing and fitting to best estimated divergence times,
but with geological timscale bounds included (which potentially introduces interesting asymmetries in the error estimates, but that is for another time).
The taxa comparison is endlessly fascinating, not all pairs work, but it is good to know that 100 Myrs separate us from Cats and Dogs both
Fun site, evolutionary genomics,
including theWest Indian amphibian and reptile database.