Definitely CynanogenMod. Probably (I haven't checked them all) the most complete and best testet Rom out there. Available for nearly every major Android hardware.

If you have a Droid X and can live without the camera, EncounterICS is unbelievably good.

It is very phone specific for ICS right now. When Cyanogen 9 comes out there will be more 'standardization.' For now, I'd look up the dev forum for your phone on xda-developers and see if there are any good options.