If you have a scanner, you can scan your drawings into the computer. I know there are some free image editing programs out there (will post later), but I mostly use photoshop and illustrator to digitize my drawings and make them prettier. If you do not have a scanner, you can also take pictures if you are going to digitize/vectorize anyway.
If you are in a financial position, the Wacom Cintiq is a thing of beauty. It allows you to use a stylus directly on a screen that shows what you are drawing. This is much better than other tablets, where you have to kind of guess? I dunno,..never really liked them much. Tablet is not absolutely necessary anyway though. I always use my mouse, and with pretty good results. The pen tool is like one of my best friends.