If you like the look of the ambient light kits that come with many cars today (or just need a bit more light for seeing inside your glove box), modder KonaStar shows us one way to do it yourself with some LED lights.
This mod isn't for the faint of heart, as it involves really getting into your car's interior (not to mention more than passing knowledge of electronics). He uses a Honda Fit, but with a bit of ingenuity you could likely use his insturctions to springboard a version for any car. It lights up the footwells and the glove compartment, the latter containing a switch that turns the lights off when the glove compartment is closed. It's cooler than it is useful, but if your glove box is difficult to root through in the dark (or if you're prone to dropping things on the floor), it could be worth more than the "oohs" and "ahhs" you get from your friends. Hit the link to see how it's done.