This simple tutorial will guide you though the steps of creating Wood Texture in Photoshop.

Create a blank 256x256 pixels document and fill it up with the paint bucket with a color like this:

Filter->Noise->Add Noise at 70% Gaussian Monochromatic.

Now it looks ok, but it can look better. Duplicate that layer and now it is up to you. Changing the blending mode of this layer will give you different effects. Color Burn, Multiply or Overlay (this one I like) will give a better look to the texture.

You can always play with the different values or colors to achieve different types of woods. Another interesting thing is to create a layer with clouds on it (Filter->Render Clouds) and use color burn. And you can use the Filter->Distort filters to create some curves on the wood.