Pen & Paper Games
has one of the better forum-built tools for finding players and games.
Players and GM's create LFG profiles that others can peruse and you can set yourself up for alerts when new profiles that meet your requirements are created. It's somewhat geared toward local games, but I've had success recruiting for online games after posting and looking through profiles for players I was interested in.
As mentioned in another thread reddit
is also a great place.
If you're not getting responses to your recruitment efforts your should look at a couple things:
1) The quality of your LFG/P posts. There might be a reason people are avoiding them. Look at LFG/P posts that appear to be getting lots of responses and figure out what you're doing wrong.
2) The popularity of the game you're recruiting for. If it's pretty obscure you should look at the publisher's own forums and be hitting up the publisher to create a hub for their users to get games together (if they don't already have one). They have a vested interest in getting players together to play their games.