This page shows the daily web browsing marketshare for mobile phones of interest, which is calculated from all mobile traffic across the 150,000+ sites that are tracked by getclicky.com. It is updated every 30 minutes.
In the past 10 days, the iPhone has been bouncing between 51% and 58% of total mobile web surfing in the US (Outside the US it’s spiked as high as 66%-one third of all non-us mobile devices online are iPhones). I’ve yet to get my hands on a Droid, but I’ve surfed the web with both Palm and Windows Mobile hand-helds and there’s just no comparison to the iPhone in that respect. Honestly, I’m surprised these statistics aren’t even more skewed in the iPhone’s favor.