www.atomicavenue.com is probably the closest to what you are looking for that I am aware of. It uses the ComicBase software as its basis, and is basically like choosing each issue you have from a massive catalog and listing the grade for it. I think the free version of the ComicBase software handles something like 500(?) issues and once you have your collection cataloged, you just tell it to upload, and they all go live on the atomicavenue website. The one drawback is that you can only list single issues (no sets or runs). That, and sales tend to be rather slow.
I use the ComicBase software myself for its comprehensive information, but no longer list on atomicavenue due to low sales volume and the troubles that arise from listing the same inventory in 2 locations (there and eBay). If you're wanting to move comics quickly, eBay is still the best way to go.
Shameless plug: I do sell on eBay and accept consignments, so feel free to shoot me a list or some idea of what you have. You can check me out under eBay ID thecatspajamas99. I've been there since 1997, and can give you a realistic idea of what to expect.