This is an extremely useful site!
I am always forgetting numbers like the diffusion limit of enzyme reaction rate in a cell especially (10^8 - 10^9 per M per sec). I had to stick something on my desktop to remember. LOLX...
Cite this pretty recent paper: Milo et al. Nucl. Acids Res. (2010) 38 (suppl 1): D750-D753.
The Gerstein Lab @ Yale also has a good compilation of Genome Statistics: