Question about mainstream sites
 

What type of mainstream sites are the easiest when it comes to building traffic? I don't mean torrent sites or warez type of stuff.

most of the threads on mainstream forums start with a recommendation that you focus on a service or product and/or niche that you yourself are into & then blog about it.

http://Nonadult.com is a rapidly growing network for you to monetize whatever sites you launch.

Are we talking porn sites? Or do you mean REALLY mainstream sites?

I mean mainstream sites. Sites that have nothing to do with porn at all.

Bump it up for a question no one will probably answer.

Online multiplayer browser games do ok and there are a lot of places to get traffic from for these types of sites

Good question. Bump.

At one time I thought about having single player browser based games. Are there any that's open source that's even worth thinking about using? I don't want to spend a lot of money on something that I know little about.

If you're looking for a lot of low commercial value traffic try "leeching off" big Web 2.0 sites by doing free themes for them. Myspace is played out, try free twitter themes. Also, metasites where you collect links that support heavy traffic/heavy interest sites are good too.

If you're looking to make real money though focus on niche blogging. Way less traffic but higher quality traffic with higher levels of commerciality.