There are tons of ways to get new visitors to your sites:
SEO - search engine optimization - comes from building real text content and trading links with well ranked sites (
http://toolbar.google.com)
Traffic Trades - such as with TGP & gallery sites - can produce a lot of bulk traffic, doesn't convert as well as seo, but with enough of it you'll make money
Affiliates - Get others to promote your program for a commission so that you can concentrate on just building your website. You won't make as much profit, but the volume can supercede many other methods.
PPC Advertising - pay per click advertising - such as google adwords, overture and a host of adult websites. Can be costly so be sure to target keywords specific to your niche.
Bulk Traffic - I shy away from buying bulk traffic as it tends to convert poorly, but it has its uses...