Party has the best and easiest to clear bonuses, so always be alert to them first (
www.bonuswhores.com)
Stars bonuses are good because they never expire and stack, so you can just grab them by depositing and clear them whenever (they clear slower than Party, but the points you earn can get you alot better schwagg than at Party)
UB is also like Stars in that they never expire and stack but they clear REAAAAAAAAAAAAAAAAAAAAAALLLLLLLLLLLLLYYYYYYYYYY slow. I always grab them (I have a big enough roll) and store them up in hopes that one day they'll make it easier to clear (they recently did the opposite, making it go from hard to very hard).
Paradise reloads are also very nice (and rare). They stack/never expire like Stars and UB but they clear a slower than Party but can be cleared at low limits (.5/1)
No other sites are really worth the reloads. Alot of people play on Absolute because they offer many many many reloads, you ALWAYS have a bonus you are workingg off, however most players there are tight and the games will be crappy.
Basically just go to
www.bonuswhores.com it has all this info much better than I can type.
And if you are signing up for a new site checking out the affliate offers is always a good idea.