Check out my latest here. It's more accurately modeled after real wood.
This is a procedural wood shader for cycles. I think it looks pretty good for the objects I've tried. You can tweak the colors in the Mix node to get different looks. Also the scale in the Mapping node might be necessary...I didn't realize this shader ball was only 11 cm. I should point out that the scene setup is NOT mine. The ONLY part I did was the wood shader.
Also, I have been trying to use this setup to make a wood plank shader (like a wood floor) but I can't get it to look good...so if anyone can do that, please do that and upload it!