Mozilla has announced the new beta version of Firefox 4 Mobile is available for download on both Maemo and Android phones. The last version was a little rough, and the developers claim to have taken user suggestions to heart in this release. Among the improvements are a much reduced install size on Android devices (17MB instead of 43MB), improved text rendering, and lower memory usage. The app also supports app2sd storage on Froyo phones.
With features like slide out toolbars, Firefox Sync, and future hardware acceleration, Firefox Mobile could really be a great browser upon completion. If you have an N900, or high-end Android phone, check out the beta.