If you enjoy traditional archery, 3 Rivers Archery is one of the best sites for components. Good customer service.
For a newer compound bow, check out Hunters Friend. Last year, I got a new Bear compound using one of their package deals that included upgraded components (you select which ones you want) and a set up (tied in peep, set draw length, set poundage, set first pin on sight at desired distance). It came with 12 arrows (I technically ordered 6) and broadheads, a release, and a soft case. The total was cheaper than the factory available Bear 'ready to hunt' package (which only includes the bow plus some basic components, none of the other stuff).
For buying/selling used gear, I've had good luck with the classifieds on Archery Talk.
