Posting Products On Comparison Sites?

When it comes to marketing your product, do you post it onto comparison shopping sites so that consumers can see if you're offering a better price than others in the same market? I've thought about doing it to market my graphic design business if I get it back up, but I don't have much experience with comparison shopping as a whole, so I was wondering if it worked for any of you.

I think it would be a great way to gain business since I'm sure a lot of people use price comparison sites to make the best decisions, especially if they're gurus in online shopping. I've used simple comparison sites like Google Shopping, but I've never actually sought out price comparison sites while selling or buying. Have they worked well for you with marketing your product?