  If you like drawing and enjoy using the computer, you might want to merge the two and explore the wonderful world of computer graphics. Depending on your computer's operating system (Windows, Mac, etc), your computer may already be equiped with some graphic programs you can start out with.
  Windows comes with a program called Microsoft (MS) Paint, which can be found by going to Start>Programs>Accessories. The supported file types are .BMP (Bitmap), .GIF, JPG (JPEG), and .PNG. While this program is limited in its features and is extremely simple in its abilities, it is a good program for creating "pixel art". However, it does not allow you to make images transparent, as other more advanced graphic programs allow you to do.
  If you'd like to try more advanced graphic programs that give you a ton of options and the flexibility you need to become a computer graphic artist, I recommend the following:

Adobe Photoshop- Raster-based program allowing you to work in layers.

Adobe Illustrator- Vector-based program

Corel Painter- Perfect for the traditional artist transitioning to the digital world. Stimulates real media.

Paint Shop Pro- Raster-based program similar to Adobe Photoshop

Animation Shop- Makes animated gifs.

There are many graphics programs out there, but these are the programs I recommend. As not to be completely biased, I've included other people's recommendations which can be found in the tools section.

Also, if you are not comfortable working with a computer mouse and prefer the feel of working with a pen or pencil, I highly recommend considering a Wacom Tablet. It's a tool designed to simulate a pen and pencil. It has the ability to draw and erase just as a real pencil. The tablet itself is pressure sensitive so you can obtain value and strokes just as you would a real pen/pencil.