|You could try posting these at Diaperswappers.com, they have a huge buy/sell section for just about anything you can imagine, they must have one for mamma pads.
Before you sell them at a loss though, remember they could be useful post-partum pads for a future new baby. Or you could use them as back-up to your menstrual cup. They'll surely be much thicker than needed for that (most just use mini liners during the day and long ones at night) but they'll still be cheaper than buying a new set of cloth liners or using sposie pantiliners. Consider too that as much as I think menstrual cups are the greatest thing since sliced bread, not everyone loves them so it might be safer (if you can manage it somehow) to keep them till you've actually tried the cup.