My husband and I are both on OkCupid... I have had plenty of interest (mostly requests for casual sex, which don't go anywhere) and met my boyfriend on the site pretty quickly. My husband has not had luck finding women okay with poly and I think it's really frustrating him. So, I feel your pain!
On OkCupid, you can do a search when looking for matches and search for keyword "poly" or "polyamory," etc. to get results of people who have listed those terms in their profile.
I haven't heard of Lavalife either, so I'm interested to try it out! Also, polymatchmaker doesn't seem to have a large or very active population, so that was a bit of a dud.