Millennial Media, one of the largest mobile advertisers in the US, has released their August MobileMix. Based on their ad impressions, they estimate that Android now commands 26% of the Smartphone market - up 7% month-over-month. If accurate, that puts Android 7% ahead of RIM - but still 22% short of iOS.
Other tidbits: smartphone impressions gained 3% in the last month, up to 51%. The original Motorola Droid surprisingly still holds 9.44% of the market as the second most popular phone (obviously, the iPhone is first); based largely on the success of the Droid, Motorola is now the third largest device manufacturer. The second most popular Android device is the Droid Incredible at 6th overall, with 2.66% of the market. In total, 6 of the top 20 devices run Android.
To quote Millennial Media, the MobileMix "reports key advertising trends with a focus on mobile manufacturers, devices, operating systems, connected devices... based on actual campaign and network data from Millennial Media." In other words, take the results with a grain of salt.
[Source: Millennial Media]