• In March 2010, there were 34 Android devices from 12 manufacturers available to consumers.
• Two Android devices, the HTC Dream and HTC Magic, collectively represented 96% of Android traffic in September 2009. Seven months later, 11 devices represented 96% of Android traffic in the AdMob network.
• The Motorola Droid was the leading Android handset in March 2010 and generated 32% of worldwide Android traffic. The Google Nexus One only generated 2% of Android traffic in March 2010.
• The top Android devices vary by country. The top three devices in the US were the Motorola Droid, HTC Dream and Motorola CLIQ. In comparison, the top three Android devices in the UK were the HTC Hero, HTC Dream and HTC Magic.

• In September 2009, the two devices that accounted for 96% of Android traffic were running version 1.5 of the Android OS (Cupcake). In October 2009, Android 1.6 (Donut) was adopted rapidly and generated 69% of requests in the AdMob network.
• In November 2009, Android 2.0 (Eclair) gained momentum with the launch of the Motorola Droid. The Motorola Droid continues to generate the vast majority of requests of Android 2.0/2.1.
• In March 2010, Android traffic share on the AdMob network was divided relatively evenly between the three primary versions of the OS: Android 1.5 (38%), Android 2.0 / 2.1 (35%)
  and Android 1.6 (26%).

• Motorola was the leading Android manufacturer with 44% share of traffic in March 2010 due to the success of the Droid and CLIQ. HTC was a close second with 43% of requests, followed by Samsung with 9%.
• Six of the top eight Android handsets have a display resolution of 320 x 480. These devices generated 60% of traffic in March 2010. The Motorola Droid (854 x 480) and Google Nexus One (800 x 480) are the two devices with different resolutions.
• At least 54% of Android traffic came from devices with a QWERTY keyboard. These include three of the top five Android devices, the Motorola Droid, HTC Dream, and Motorola CLIQ.
• 92% of traffic came from Android devices with a CPU slower than 600 MHz in March 2010.

From: http://metrics.admob.com/wp-content/uploads/2010/04/AdMob-Mobile-Metrics-Mar-10.pdf