i've used a couple of overdrives, a Marshall Guv'Nor and a Thundertomate Overdrive+ mainly, both with very good results. the only actual booster i've spent time with is the Thundertomate Phil Hilborne fat treble booster, and it is a fabulous pedal, with the right amp. masses of great sounding boost, and can push a barely ticking over amp into screaming distortion! i recently tried a Carl Martin Hydra Boost through a late sixties Marshall head, and it sounded awful. i've just bought a Keeley Time Machine boost, but it's just arrived and i haven't tried it yet.
so the simple answer :) my favourite boost, so far, is the Thundertomate Fat TB.