One of the first things you should do as you plan you basement project is take measurements. This will help you decide what should go where, and what you can fit in your basement without it appearing too crowded.
Try using graph paper to draw your basement to scale, or use an interior design program to help you draw and design your finished basement. If you want to try graph paper, download it here or get the .pdf version.
When I decided to do this site as a chronicle of my progress, I figured I'd need some decent images to put on the site. I also wanted an interior design package that would allow me to move walls and change color schemes and decor. After reading reviews of both Punch! Interior Design Suite and Better Homes & Gardens' Interior Designer (now called Chief Architect Home Designer), I went with BH & G.
In addition to being able to add furniture, lighting, and other decor, the software allows you to create 3D views and walk-throughs that help give you a better idea of how your final design will look. Here's what I came up with as my 'final' version.