According to IDC (as presented by Fierce Wireless) the top selling smartphones in the US in Q2 were:

1. BlackBerry Curve (available through all US carriers)
2. Apple iPhone 3GS
3. BlackBerry Pearl (but not Flip version)
4. Apple iPhone 3G
5. BlackBerry Bold
6. BlackBerry Storm
7. G1 by HTC (Android)
8. Palm Pre (Palm/WebOS)
9. HTC Touch Pro (WinMo 6.1)
10. HTC Touch Diamond (WinMo 6.1)

According to comScore, here's the market share distribution of smartphones by OS in the US:

Source: comScore (May, 2009)

Here's AdMob's network representation of US mobile Internet browsing market share by mobile OS:

 Source: AdMob (June, 2009)