Peter
If you're running Linux and your distribution hasn't yet updated your software packages to upgrade you to Firefox 2.0, here's a really quick tutorial on how to upgrade yourself.
Head over to getfirefox.com and grab the latest Linux version for your language. It should be already selected on the download button, but if not, head to this page and choose the right version for you.
Once you've downloaded that, you'll have a firefox-2.0.tar.gz file. Simply extract this somewhere suitable (move it to a suitable folder, then right-click it and choose Extract Here, or the equivalent option).
Now, it's time to make a shortcut on our desktop that we can use to start our customised Firefox installation.
In Gnome
Right-click on your desktop and choose Create Launcher. Fill in the fields so they're like the image below (changing the command to match the folder you put Firefox in, followed by a slash / and then the word firefox).
OK that and then you can use this shortcut to start Firefox 2.0.
In KDE
In KDE, right-click your desktop and choose Create New > Link to application. Type Firefox in the name field and then go to the Application tab. In the Command box, type the path to the folder you put Firefox in, followed by a slash / and then the word firefox.
Now, just use your new shortcut to enjoy Firefox 2.0 (until your distribution hurrys up and updates the packages!).
Enjoy!
UPDATE: I've also done a screencast of this, so if you want to actually see it being done, watch it now!
