GCC Optimisations per CPU
Written in 2007. Versions, commands and links may well be out of date.
Pádraig Brady wrote a very useful script for getting the optimum gcc options for your CPU which I keep coming back to (and forgetting where to find it).
The last version can be found at http://www.pixelbeat.org/scripts/gcccpuopt along with a lot of other useful scripts and scripting examples here.