An alpha release of Firefox Mobile (dubbed Fennec) has been around for Maemo-based Nokia devices since October 2008, but according to an update at the Mozilla Wiki, a milestone update will see the browser start hitting Windows Mobile devices as soon as next week. Initially Mozilla is targeting the HTC Touch Pro only but Fennec is expected to appear on other Windows Mobile devices over the forthcoming months.
Details are scarce at the moment but expectations are certainly high - especially with Microsoft refusing to offer mobile IE 6 as a standalone update but rather making it available with new phone purchases only. According to Mozilla's own Acid 3 test, the preview release of Fennec achieved a 88/100 score running in Windows Mobile, which compares favorably to the iPhone's Mobile Safari browser score of 74/100 on firmware version 2.2.
Anyone who's just curious about what Fennec will look like can test it out on their desktop as well by installing the appropriate version for Windows, Mac OS X, or Linux.