• by Mark Walsh  @markfwal, June 3, 2011

Android continues to extend its lead over smartphone platform rivals, with its share of the U.S. market increasing to 36.4%, on average, for the three months ending in April. That marks more than a five-percentage-point gain from the 31.2% share the Google mobile operating system had for the prior three-month period ending in January, according to the latest comScore data.

Apple's iOS, the next-largest smartphone platform, increased 1.3 points to 26% as of April, a full 10 points behind Android. Research in Motion's BlackBerry OS continued to lose ground, dropping nearly 5 points to 25.7% and virtually deadlocked with iOS. And Microsoft has yet to show any share gain from the launch of Windows Phone 7 last year, with its slice of the U.S. market slipping from 8% to 6.7% from January to April. Palm's webOS had just 2.6%.

When it comes to phone manufacturers, the relative share of the top players was little changed from January. The biggest gainer was Apple, which grew its share from 7% to 8.3%. The company sold 18.7 million iPhones during its second fiscal quarter ending in March, more than doubling the total from the year-earlier period.

Samsung, however, continued to lead the category overall, with 24.5% share as of April, down slightly from January. LG followed with 21%, and Motorola, 15.6%. RIM slipped just behind Apple at 8.2% to round out the top five.

The comScore figures released Friday also showed that a growing proportion of mobile users are using their devices for a variety of activities. Nearly four in 10 (39.1%) browsed the mobile Web, almost 38% used downloaded apps, 28% accessed a social networking site or blog, and 26.2% played mobile games.

Usage in each of those categories was up at least 2 percentage points in April compared to January. The 18% who listened to music on mobile phones was up 1.5 points. Texting remained by far the most popular mobile data activity, with almost 69% penetration.