The April 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 April 2009. The list measures the number of unique individuals or sources that posted content about each brand during April 2009 rather than the overall number of mentions, which would be more heavily influenced by big fans who post frequently about a specific brand.

Twitter once again dominates the Top 50 list in April 2009. Already the hottest brand on our March list by a wide margin, Twitter accumulated an additional 10% in chatter in April.

Content sharing website Digg joined the Top 50 this month thanks in part to the April 2 launch of the DiggBar. Enterprise software company Oracle also joined the list with an increase in chatter due to its April 20 acquisition of Sun Microsystems. And as the NBA and NHL Playoffs heated up in April, the NHL joined the Top 50 while the NBA jumped 9 spots.

Dell dropped 23 spots this month as buzz around the March announcement of the new Dell Adamo faded. Kindle also dropped out of the Top 50 as hype around the Kindle 2 subsided.

Conversely, CNN jumped up 10 spots thanks to the race to a million Twitter followers with Ashton Kutcher. IBM also jumped four spots thanks to increasing focus on social media.

View the list below, or download the full 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.