I've been playing around with Opera Mini. If you haven't heard yet, Opera Software ASA has released a Java ME (J2ME) version of their browser called Opera-Mini. Opera is the Norwegian company who make the browser of the same name for many platforms. All their browsers have a technology they call small screen rendering™ which reformats full desktop web pages for display on tiny phone screens. The reformatting works remarkably well - although reformatted pages aren't likely to be as easy to navigate as well designed mobile pages.
The Java ME part means that you don't need a smartphone to run Opera anymore. Most phones made in the last three years support some version of Java ME (which was called J2ME until Sun renamed it this year). Non-Smartphones generally don't have the processor power and RAM to do all the manipulation that is required to implement small-screen rendering. Opera Mini gets around this by doing the reformatting as a web service, the Opera server resizes images and optimizes the page for the phones screen size and then compresses the resulting mobile page into some sort of binary code which the Java ME app on the phone can easily render. The result is that pages load quickly even on old slow phones. This also means that Opera can easily start charging and shut the service off for anyone who doesn't want to pay the price. But for now at least it is completely free.
Opera Mini won't run on every Java ME phone, there are a lot of incompatibilities between Java Me implementations but I believe it will run on the majority of them.
By now you are probably asking, "how much?" and "how can I get Opera Mini on my phone?" The good news is that for now at least, Opera Mini is free. The bad news is that it is only officially available in Norway. You can read about it on the official Opera Mini page. Fortunately for all of us, who don't live in Norway, the application has been "liberated" and can be downloaded from a number of sites on the web. The legality of these copies is, of course questionable although a mainstrean Palm site is among the many places you can find the download. If you want to try it yourself, be aware that there are two flavors of Opera Mini, "lo-fi" and "hi-fi". The differences between the two are that lo-fi is MIDP1.0, essentially the first version of, Java ME and hi-fi is the latest version MIDP 2.0. MIDP 2.0 is backward compatible to MIDP1 so if hi-fi doesn't work on your phone be sure to try lo-fi. Opera has a list of supported phones by version but I don't know how accurate it is, as it doesn't work on my Moto i50sx which is on the supported list. The only apparent difference in features is that hi-fi adds font- smoothing and the fonts do look a little nicer, although the lo-fi fonts aren't bad at all.
Opera Mini has been confirmed on various web sites to work on SE K750, S710, w800, Nokia 6100, 6320, Motorola V330, Razr V3, Palm Tungsten C, Treo 600, Treo 650, Tungsten T3, Zire 72, Lifedrive, Sony Clie TH55-U, UX-50. Palm OS users need to first install a KVM (Java ME virtual machine) from IBM or Palm.
Here are images of MSN, Yahoo, HowardForums and Flickr's web sites as they appear in Opera:
Opera Mini download links:
These first four are a slightly later version (1.0.1520 v 1.0.1479) then I've found anywhere else although I don't see a difference in functionality between versions. If you phone supports installing Java ME midlets OTA you should just need to point your browser at the JAD file. If you are 'side-loading' from your PC via bluetooth or cable you will need both the JAD and it's matching JAR.
Lo-fi JAD Lo-Fi JAR
Hi-Fi JAD Hi-Fi JAR
An alternate source which has all the files as a .RAR archive and also individually but they are the older version: Bluemonkey.org
Finally, a link to a Treo compatable .PRC file (free registration required to download)