Michael's Traffic Videos: very useful series of well thought out videos outlining various traffic generation techniques. (Michael Cheney. Membership Site/Videos)
Piggy-Back Traffic: good method of getting high ranking and even first page Google listings and the massive influx of traffic that brings through a combination of authority site listings and article marketing. (Ryan Deiss E-book)
Secrets of Traffic: a nice (and cheap, only $12 at the time of writing) E-book by top traffic generator Peter Bray that walks you, step-by-step, through 12 techniques that are guaranteed to increase traffic to your website. (Peter Bray. E-book)
Traffic Imperium: how to set up a system that will drive thousands of keyword specific visitors to your site. (Joern Lillehagen E-book)
Video Traffic Power: learn how video can be used to drive visitors to your site. (Jonathan Leger. Videos)
Building traffic using user submitted content
Munius: software makes it easy to create an article directory on your site and accept automatic article submissions. (James Brausch. Software)
Building traffic using doorway/entry pages
Website Article Wizard: software produces hundreds of unique pages from one article. (David Watson. Membership Site)
Website Content Wizard: rewrite articles quickly with this software. (David Watson. Software)
Selling Traffic
Trafficopia: system that allows you to sell advertising on your content sites. (James Brausch. Software)
Traffic Exchanges
HitPulse.com: traffic exchange with over 100,000 active members. (Logiscape Technologies Inc. Membership Site)
TheHitsMachine.com: for each 4 sites shown in your browser, you will receive 3 hits in return. (The Hits Machine Membership Site)
TrafficSwarm: get live, real-time targeted traffic from this #1 rated exchange with over 300,000 members. (TrafficSwarm Membership Site)