Thinking of renovating your basement? If you are you'll need to make sure you have a dry basement which I explain how to achieve in the tutorial Troubleshooting a Wet Basement.
Turning basement space into "lower level" living space is a great way to improve the usefulness of your home. As you see in this blog's photo of my home's basement, lower level spaces can be fun and attractive.
A great website I've found that has some very useful videos on finishing out a basement is called Armchairbuilder.com. This website is a great reference for folks looking to do their own construction for new homes, additions and major repairs. They have a very nice how-to video library on basement finishing including pre-planning, moisture control, bidding to contractors (see also Dealing with Contractors), mechanical, insulation, tiling, carpeting and other aspects of basement renovation.