I can't seem to find an official announcement, but a new beta version of Opera Mobile 8.65 for Windows Mobile is available directly from Opera's download site. This release is notable because it (finally!) includes a version for Windows Mobile 5 Smartphone devices. To install Opera Mobile on a Smartphone device: download and run opera_wm5_sp_865b.msi, then restart your phone.
The Minimo team also had a recent new release: Minimo 0.2 includes a bunch of new features and bug fixes, and adds support for Windows Mobile 5. Minimo has an impressive set of features--JavaScript/AJAX support, RSS feed reader, tabbed browsing and a widget engine, to name a few--but it seems to be having a very hard time gaining traction. In fact, despite the new release, Minimo's future is far from certain. In December, lead developer Doug Turner announced he would be spending less time on Minimo in the future. On his blog he wrote, "there are lots of browser in the space, the market is tightly control by cellular operators, and the end users aren't using the browser. This will change, but not for a few years."
Microsoft Labs also made waves last week with a very limited beta release of a new browser named Deepfish. Deepfish is a Windows Mobile-only browser that works like a cross between the iPhone's browser and the S60 browser. It uses a proxy to generate a zoom-able web page interface that mimics the appearance of browsing on a desktop. The Deepfish Demo looks great, but the browser is barely usable in its current state: no support for cookies, JavaScript or HTTP POST.
Can't decide on a browser? Axim Site has a head-to-head review of Opera Mobile, Minimo and Deepfish.