I'm posting more about fonts then I am about programming, it seems.
So, let's say you're making a racing game. You'll probably need a font to accurately represent the signage if you're to have races take place on any highway.
The traditional font recommended by the United States Federal Highway Administration is known as Highway Gothic. Some free "close enough for government work" fonts that approximate it is listed at the bottom of the Wikipedia article, but most are free for personal or hobby use, which isn't good enough licensing for open source games.
However, one font that IS friendly is Red Hat's Overpass font, found in Fontspace's Highway category. It is SIL Open Font License, so you could even use it commercially if you want.
Incidentally, the NEW font (which isn't yet adopted everywhere in the States) is known as Clearview. I have yet to find a free version (open source friendly or not) which approximates it.
