Saul Hansell of the NY Times does a good job describing Google's new behavioral advertising features. I would add one more company, WPP's Safecount, to the list of those showing user's their profiles. Safecount is in the research/analytics business, not directly in behavioral ad business, which is probably why Saul didn't include them. However, the reality in the industry today is that all the data business models are beginning to converge as data collected on one platform is also available for other uses. Consider for example Revenue Science (now Audience Science) which started out serving individual sites, but now has expanded into also acting as a behavioral ad network.
One other point that we like about Safecount is the way their home page is structured to serve both individuals and businesses. Most ad networks or analytics companies have corporate sites geared toward recruiting new business partners, with a small privacy link at the bottom that leads to consumer privacy information. But individuals visiting an ad network home page aren't looking to buy ads. Individuals visiting these sites are there to learn about how web surfing data is used and perhaps how to opt-out. Safecount sets a good example by recognizing the dual audience they serve and sets a great model for transparency by providing precious home page space to communicating with consumers. Data sites that aren't ready to go as far as Safecount by splitting their home page between their two audiences might consider atleast putting their privacy link in a more visible location at the top of the page.
A more prominent communication about data use is certainly something every Web site ought to be considering, but companies in the data business who want to be more transparent should take particular note. Check out also the prominent "CONSUMER" tab on the Blue Kai home page and the Opt Out link on the TruEffect home page.