If you use Firefox, you know that your browser has problems with memory leaks and will eat even 200 MB of RAM at times. I hoped that Firefox 2.0 (Bon Echo) will fix this issue, but unfortunately it's not the case, as this version focuses more on cosmetic issues. So I've decided to try the alpha version of Firefox 3 (Minefield), that is developed in parallel with Firefox 2.0. And the results are incredible: the browser has never consumed more than 70 MB of RAM even with 10 tabs opened.
This version of Firefox, due to be released next year, has more rendering problems than Firefox 2.0 and doesn't have too many new features (the most notable are Places - a unified interface for bookmarks, history, feeds, and a new data storage layer for bookmarks and history that uses SQL), but the memory management is clearly superior.
If you want to read more about the new features of Firefox 2.0 and how to make your extensions compatible, read this small review. Most of the things are still available for Firefox 3.0.
You can install the latest build of Firefox 3.0 from this page. For example, the Windows version can be downloaded from here [5.8 MB].
Remember it's an alpha version, so if you have problems, uninstall it and continue to use your current version of Firefox.