Funny, I came along at the same time you did, looking for sourdough bread recipes. Some people will tell ya that the starter is the "hard part". Here's what I have done in the past, with great success (in fact I just did it AGAIN after a few years).
2 cups white flour (regular bread flour)
2 cups plain ol' water
in a bowl that is NOT METAL (apparently, that's really important), mix together the flour and water. Use a wooden (or plastic) spoon, or a spatula.
The fun part: use a piece of cardboard (the lid from a shoe box will do nicely) and "fan" the bowl for a while. If you don't have a shoe box lid, use something similar. Let your imagination run wild. This will accelerate some airborne spores into the mixture.
Use a piece of cheesecloth, and stretch the cheesecloth across the mouth of the bowl, holding it in place with a large rubber band. I didn't have any cheesecloth, so I used a piece of cotton cloth (I think it was once a pillow cover), which I cut into a 12"X12" square. The idea is to allow air/spores/other goodies to circulate, while keeping out cat hairs, golf balls, and whatever other things might be flying around your house.
Put the bowl with the mixture in a (fairly) warm, safe place (I have mine on top of my upright freezer). After about 24 hours, give it a stir. Put the cloth back on, and wait another 24 hours. After 2 to 3 days of this, the mixture ought to have a bunch of little bubbles in it, and it should have at least a faint sourdough smell. Yay, you've got live bacteria!!
If my starter took (for example) three full days to begin to ferment, I'll wait three MORE days (stirring daily), then add 1 additional cup EACH of flour and water. If it takes 4 days to start to bubble (or 5 or 6), then so be it; I can wait.
After the additional flour and water, the same strain of lactobacillus bacteria will continue to reproduce (although they might be augmented by some additional strains that you didn't know existed in your kitchen). The combination of flour (and water) and yeast creates an inhospitable environment for other types of bacterial growth.
Divide about one-third of the starter "sponge", and keep it in a covered container in the fridge. The remaining couple of cups is what you use to bake your bread. When you want to re-create (at least, very closely) the starter, you just repeat the process with the small amount of sponge you've retained in the refrigerator.
Now, all I need is a butt-kickin' recipe
Best of luck!