Years ago, Mozilla introduced its mobile equivalent of Firefox, then-called Minimo. Minimo unfortunately largely died of boredom within Mozilla. In early 2008, however, , and the heavens rejoiced (though even the heavens couldn't get it installed on [Name your mobile device of choice]).
As recently announced by Mozilla, however, Fennec just hit its second alpha release, with the option to download and install the mobile browser on Mac, Linux, and Windows desktops for testing purposes. (If you want to install it on your mobile device, you're going to need to have a Nokia N810 device on which to install it.)
Alpha 2 has made significant improvements to Fennec's performance (e.g., Faster panning and zooming plus improved responsiveness while pages are loading) and ease-of-use (e.g., Bookmarks, tabbed browsing with thumbnails, etc.)
As Fennec development continues to move forward, the value and significance of having the complete Firefox stack in a mobile environment is becoming increasingly apparent. Developers have already started creating innovative add-ons for the new browser that increase its functionality in various ways. For example, the TwitterBar extension allows users to post to Twitter directly from the Fennec address bar. An early Fennec port of Mozilla's Weave framework is also underway.
Like Apple's iPhone rendition of Safari, Fennec may well prove to be most disruptive when replicating and extending the desktop experience in a mobile device. This is where open-source Fennec could leapfrog its proprietary competition, including the iPhone's Safari.
Just as Mozilla's desktop Firefox set the pace for what a desktop browser can be by tapping into a disparate, global community of hackers with their own assumptions as to what a browser should mean so, too, can Fennec become the mobile browser's innovation leader by letting users define the experience, not any single company.
Much as I love Apple, I almost never use its Safari browser. If Mozilla can get Fennec right, I suspect I won't be using Apple's iPhone browser, either.