if you're out of town a lot and/or you don't have time to fill orders yourself, or you don't want to fill orders yourself and want a more "hands off" way to have your clients order, Pictage is a great resource. It's a lot like
collagesand
smugmugand
printroomand
eventpix (eventpix & collages are a bit different in that you have some choice when it comes to where the prints are done)
there are others, too, but those are the commission-based ones that come to mind.
They're basically an online ordering system where your clients order, they fill the order for you, and you get a check with your profits (minus their commission & the cost of good sold). Commissions usually range from 13-18%
They also have varying fees (sign up fees, monthly fees, per image fees, per event fees). They're all similar yet different, so you have to look at them all and see if any of them are rightfor you & your business.