I want to be able to use an actual NES (or, SNES) controller to control an emulator on my PC.
Is this possible?
If so, how can I do this on a budget?
RetroZone has a product which adds a NES port to your computer via USB. Also, you could buy an already converted NES controller which plugs directly into your USB port. (They also supply the same products for SNES.)
As for converting a controller yourself, Joystiq has a tutorial but it involves buying a kit from RetroZone.