gumtree appears in a lot of the SERPs I'm starting to look at and it accepts business listings free, with the irritation that you have to target regionally. Its on my list to have a look at for automated submission for one client but I haven't got to it yet.
There's also a host of others like friday ad, viva street, preloved but it does seem to depend on your search terms how much you see them - having never used craigslist I'm not sure exactly how similar these are but I think they're all along the same lines.
If you're looking regionally some areas also have a lot of local sites which rank well and may take ads if they can't do a listing how you want one. Likewise niches.
