The May 2009 Social Radar Top 50 measures the brands with the most active Web presence based on overall online conversation volume. To create the Top 50 list, we used Social Radar to analyze millions of blog posts, news feeds, forums, social networks and Twitter posts to aggregate a list of the words and brands mentioned most frequently on the Web during May 2009. The list measures the number of unique individuals or sources that posted content about each brand during May 2009 rather than the overall number of mentions, which would be more heavily influenced by big fans who post frequently about a specific brand.

The top six brands held their positions in this month’s list. Twitter, Google, Obama, iPhone, Facebook and YouTube remain strong with increased buzz across all online mediums. Windows jumped past Mac this month thanks to buzz on Windows 7. Linux moved up two spots, while the NBA jumped six spots thanks to an exciting month of Playoff games. The NBA’s active Twitter account has nearly 700,000 followers, and several players are also tweeting. Notably, @dwighthoward, who gave a shout out to his Twitter followers in a post-game interview, has quickly amassed nearly 200,000 followers and has been called the next big ad man by Ad Age.

Dell jumped 22 spots thanks in part to a new Studio line of laptops, as well as the continued growth of @delloutlet, which has nearly 600,000 followers on Twitter. BlackBerry jumped five spots, corresponding with their strong sales — BlackBerry Curve is outselling iPhone so far in 2009. Nintendo dropped 8 spots as some of the video game chatter shifted to Microsoft’s Project Natal and Sony’s Motion Controller.

View the full list below, or download the PDF. For additional information about how you can analyze chatter sentiment to gauge positivity/negativity, view key words mentioned about your brand and identify key influencers, visit www.infegy.com/socialradar.

Questions or comments? Twitter me @adamcoomes.