In the US, the next closest mobile platform is RIM with 12% and WebOS with 5%. Bringing up the rear is Windows Mobile with 4%, other at 3% and PalmOS at 1%. To be fair, Windows Mobile just launched WinMo 6.5 which comes with a decent browser compared to the comparatively useless browser that WinMo 6.1 and earlier has. We may see increases in WinMo share in the coming months if sales are healthy. Android isn't likely to suffer though as there are a flurry of devices with Google's platform launching even now.
If this information is of interest, you should check out the entire report. AdMob has provided a lot more data by platform, carrier and device maker in various locations around the world. These stats really tell who is enjoying using their device. There is nothing worse than browsing the web on an underpowered device with a slow connection and weak browser.