Biggest challenge is getting buyers and shoppers to your site.
Ebay is one venue for this - which is what I've been researching for the past couple of months.
Another is Froogle. Turns out an OSCommerce store can upload directly to Froogle - and your entire store has now just become international for free.
There are probably venues which get buyers to your store. (Amazon would be one, except it has a high-priced annual entry fee - you think they'd lower the bar to attract more sellers who could be upgraded to that annual fee...)
The trick and sequence is to get them pre-qualified by having them buy to begin with (some call this a "reverse funnel") and then turn them into repeating customers through quality service and free/paid subscriptions.