are you looking to buy leads or do you want people to promote something for you? the reason i ask is i think somewhere on this harddrive of mine i have a list of networks that people can sell their leads to and others can buy them. its mostly for when you have for example 10 autoresponder messages set up and someone has gotten them all now what do you do with them? if that helps at all let me know and ill try to dig up the list for you. if not...no biggie.
Then how about you get an auto responder, make a squeeze page, and promote in venues that will draw that crowd onto your list.
Not really the forum for email list experts but you can probably find more than enough candidates through a Google search.