It was recently announced that Firefox Mobile ("Fennec") was going to be a reality, and it appears that development is now steadily progressing. 
Brad Lassey has a bunch of screenshots up at his blog, including some basic pages as well as Acid3 run to demonstrate he has the full browser running!
Exciting stuff, especially as Firefox Mobile is likely to support kinetic, touch-based scrolling as per this concept video. As far as I can tell, these are just development snapshots, and no public binaries are actually available for download... yet.