First, the obligatory "every Droid is diff and diff kernels work better with diff Droids".
I was using the Golden Elegance theme and I tried the stock, Chevy's, Jake's, and jdlfg's. Jake's performs the best for me at 1GHz, but I can get to 1.2GHz with jdlfg's, given me better performance (however, only slightly over Jake's 1GHz). Not every Droid can get up to 1.2 and 1.25GHz, but if you can handle it, I recommend Jake's. GirLuvsDroid compiled a list of known available Froyo kernels that you can find in the stickies. When it comes to kernels, trial and error is really your only option.