Polling for Dollars The use of the web as a medium for market research is often ignored - perhaps its not sexy enough - but here is a good example of the possibilities.

Email Competitive Analysis As the author of this piece says, we've always done this in an offline environment - but does anyone else feel uncomfortable inventing a persona to register on a site?

I think that there is a reasonable argument that online research is the most effective way for marketers to use the web, here's an example - How Mercedes uses online research communities.

This article - Focus Groups 2.0 - suggests that social networks can be a more modern, more interesting, and less expensive way to conduct focus groups.

This article - How to Hear the Voice of Your Customers: Hone First-Person Intelligence From All Forms of Feedback - is quite deep [as befits its author], but it is an excellent read on how best to analyse and use social media content as part of an organization's intelligence-gathering efforts.