Nice site. I would suggest removimg the top banner ad, you will make more money from sales then losing potential customers for pennies. Also, it will make the site look cleaner and allow you to use the space for a better logo. The logo does not a little work.
Other than that, I would suggest changing the dark green-brownish collor of the sidebar block titles. It does not really match the overall color scheme of the site and is not pleasing to the eyes.
Overall I think you are on the right track!