According to the blog of a Mozilla employee, the company has released a "Milestone Release" of the Fennec browser for Windows Mobile. The program can be downloaded for free but there is a catch. Right now, the only device that this will work on is the HTC Touch Pro. The program was rushed out in order to get feedback from users and the browser and extensions will not update. Plug-in support has been disabled and there is no soft keyboard support. Also, there will be no automatic updates for users, so you need to keep your ear to the ground when it comes to further news on the browser. Remember, this is not a final build-not even close. If you choose to download it, not only will there be bugs galore, but the software might not work smoothly. The browser has been highly anticipated and is a "high priority" item for Mozilla. The blog has a link to install this release of the Fennec browser.
source: Mozilla's Brad Blog