InsideCRM has delivered an excellent article for business owners and marketing professionals seeking to explore and capitalize on Web 2.0.

50 Social Sites That Every Business Needs a Presence On covers the industry leaders, including Digg, LinkedIn and YouTube, as well as niche sites and upstarts, such as Ning and Sphinn.

I highly recommend bookmarking the article, and spending a few hours browsing to see what these social sites have to offer your business.