This depends on the project. I'm a non-visual person myself. If it's open source or non-commercial then I recommend http://www.oswd.org -- I have to admit your site will look very Web 1.0 but I've had luck outfitting my open source projects from here.

I'll second what others are saying: you should learn HTML, CSS (properties, selectors, box model, etc.), and become competent with Photoshop or The GIMP.

These skills let me modify (with mixed results) existing templates. They also save me money when working with a designer. I'm able to provide direction by modifying his mockups saving time (= $$$) and confusion in the process.