there are a number of options available to you, and i'm sure others will jump in, suggesting sites that have or have not worked for them.
i've been using exposure manager
for about 5 years now and they haven't given me any reason to leave. the things i like about them are:
- they offer private label branding, meaning that i can customize my site so my visitors see only what i want to them to see.
- they offer self-fulfillment, meaning i control what goes in the package and make more money by using my local lab.
- they allow me to upload low-res images for the galleries, but allow me to sell whatever size i want
- they have reasonable fees, about $100/yr and 10% commission
- they pay by direct deposit, monthly
while they might not be the end-all-be-all, they have served me well and i highly recommend them.
you should keep in mind, though, that having an online gallery is not an automatic ticket to making money. it's extremely competitive. you need to not only build up an inventory, but to keep it fresh, adding to it on a regular basis. you also need to promote it. one key decision you have to make is whether to try to make money off the volume or the margin (that is, hoping to sell a lot with really low prices, or selling few but with great markups).
good luck!