Just as Mozilla's developer wiki cryptically promised last week, a pre-alpha build of Firefox Mobile 'Fennec' has been made available for the HTC Touch Pro, though it'll work on many other VGA (480x640) WinMo phones.
The build is very rough and probably not usable for day-to-day browsing—early reports suggest that the loading time is very long, and that page loading is quite slow pretty much broken—but it might provide a glimpse of where Firefox Mobile is headed, how it will render pages and if its novel control scheme is usable on a device smaller than the N810.
The CAB download is available here, but I had no luck launching the app on my T-Mobilized HTC Touch Diamond variant. Let us know about your successes and failures in the comments. UPDATE: A consensus has emerged! It's not at all ready yet. It's to be taken as an assurance of forward movement, I guess. [WMExperts via Slashphone]