Sara Ford, a Software Design Engineer in Test at Microsoft, has posted a set of macros which allow you to easily tweak fonts and colors in the VS.NET 2003 IDE. These macros were intended to automate accessibility testing, but there are two in particular which are really handy for general use. As Sara says:
Even if you don't use Accessibility Features, definitely check out the Increase and DecreaseTextEditorFontSize macros. These simple macros will allow you to painlessly increase and decrease the text editor font size by assigning a keyboard shortcut to each macro.
These two macros are really handy for when you're conducting a presentation, switch to Visual Studio.NET and have to dramatically increase your editor's font size so the attendees in the back row can read your code.
Download the macros here.
Update: These macros are installed by default with VS.NET 2005 (thanks for the feedback, Sara).