Employers will occasionally debate the relative merits of various forms of finding good employees -- the web, job fairs, third party recruiters, newspaper ads, employee referral programs, etc.
As the talent pool diminishes, even while the need for skilled workers increases, I don't think you can choose favorites. Effective recruiting requires a variety of channels.
Even just your online efforts should mix things up. Now that the web has become the cornerstone medium on which to post jobs, you can't afford to choose just a single employment Web site. If you really want to cover all the bases, start with the strongest local employment Web site you can find. (Start here.) For somewhat specialized positions, find the best "vertical" (industry-specific) employment site you can. If supply and demand require you to expand your search nationally, add one of the big national sites to your arsenal.
You can complement these efforts by Web-based searches for candidates. Web-based networked like LinkedIn.com are great. Industry-specific online networks like ere.net (for recruiters and employers) can be useful. Creative techniques include searching the Web (and "blogosphere") for candidates with the right skills.
Meanwhile, complement these channels with non-internet based efforts. An employee referral program is a must. Job fairs and networking events where you can target the right type of candidates and meet them face to face are also invaluable.
Finally, the cutting edge of recruiting (especially as things get increasingly competitive) is employer branding. This blog will continue to expand on this important subject. Your employer brand can dramatically enhance your recruiting efforts. It can also undermine them. Here's one tip: work with employment Web sites that offer features that help with your employer branding, rather than just posting your jobs. (Again, start here for a network of sites that offers several powerful tools.)
Even if your recruiting efforts are going pretty well, don't wait for the "war for talent" to really get going. Establishing a diverse portfolio of recruiting channels will pay off in the years to come.