I am a beginner as well. I have a pair of wooden needles, and another pair of the Boye aluminum which I picked up at JoAnn/Michaels. I actually prefer the aluminum because of the slide factor. It seemed like when I was knitting with the wooden needles, the yarn would bunch up and it would be hard to move it up/down the needle and I'd be pulling at it.
But, I know of 2 other women who are in my knitting classes, beginners like me, who are using bamboo, as well as wood.
As redwitch & VickyS456 said, go out and buy some cheap pairs and find what you're comfortable working with, that's how I am working it now. Just always make sure to hang on to the yarn you're working and it shouldn't slip!