depends. if you have low volume, paypal is really going to be your best option. i was rejected from merchant accounts for low estimated volumes. if you have higher volume, any merchant account will do, really.

consider using something like chargify, spreedly, cheddargetter, etc. to manage subscriptions and such. most also provide a nice professional interface for things like paypal.

HN superhero patio11 suggests spreedly+paypal.