I came across this article some time ago and always needed a reference to it.

So I thought I’d pin it to my mental noteboard in the sky for all to share…..

http://technet2.microsoft.com/Office/en-us/library/6a13cd9f-4b44-40d6-85aa-c70a8e5c34fe1033.mspx?pf=true

Great article on how much MOSS/WSS can handle, from speed differences with site enumerations
through to max elements in lists and doc libraries. Some very good numbers

Enjoy!