VMWare Fusion 1.x defaults the emulated mouse to a bog-standard 3 button wheel mouse (in Windows guest operating systems.)
VMWare Fusion 2 (beta 1) now emulates a multi-button mouse, which essentially means "back button in a browser" support.
I have a Logitech VX Revolution mouse on my MacBook Pro, but these steps probably apply to most Logitech mice in general, and other USB mice besides.
On OS X, there is no standard application behavior for what on Windows are called "XButtons", buttons 4 and 5, generally located either on the left side of the mouse, one on each side, or on the right side of the mouse for left-handed mice.
On Windows, many applications (which means "Browsers") translate Button 4 clicks to "back in history" and Button 5 clicks to "forward in history", following Microsoft's lead when the IntelliMouse came out in the late '90s.
On OS X, applications seem to be converging on command-[ / command-] as the shortcut keys for back/forward, so if you want mouse support for this you need to get your mouse driver to send key presses on these clicks.
The standard Logitech OS X driver, called "Logitech Control Center", sucks. No really, it sucks: it installs a Input Manager hack and doesn't play well with other applications.
What you want to do is use SteerMouse or USB Overdrive, which are 3rd party generic USB mouse drivers. Either of these apps are so go good you wonder why Logitech bothers writing their own driver at all. They should just OEM one of these.
For what it's worth, I ended up buying SteerMouse, for reasons I don't quite remember. (I think it recognized "button 6" on this VX Revolution, where USB Overdrive didn't.)
So with SteerMouse:
The result will be back/foward support in OS X and Windows guest OSes. (Note, may not work in multi-monitor full screen guest Windows.)
Woot.
(If specific OS X applications have different shortcut keys for back/forward, you can of course add application overrides for them as well.)
