I haven't attempted this, but I think a better route than listing on Flippa (or another site) would be to seek out a strategic buyer, someone who would see $1,500 of value in the website. This could be someone who wants the users, or just the application. To justify $1,500 it seems buyers on Flippa would want a few hundred in monthly revenue at least, and stable too.
Again, I haven't tried this, but what about looking on Elance and other marketplaces for people who are looking to build a similar site. Offer to sell the site and consulting services to set it up for them. To them, the value of a tested application would be worth well over $3k I'm sure.
By the way, I'm in a similar situation with OrangeSlyce.com.
Do you have any suggestions on other places to sell?