This one has been often blogged but a good tip came around on email to use Consolas mono-spaced, clear type font inside Visual Studio. I’ve been using it for a little while and think it looks great. You can download it from MSDN. A good visual comparison between Consolas and the standard Courier is here.
One thing to add is that it’s optimised as a clear-type font. In Vista all fonts are enabled in clear type by default, but at least on my XP machine they weren’t. To enable this you need to go to the display properties dialogue (right click -> Properties on the desktop). Then on the Appearance tab, hit the Effects button to find this dialogue to enable it.
In Vista you can find this dialogue under Control Panel\Appearance and Personalization\Personalization on the Window Color and Appearance item. Use the link to open the classic properties box.