If you want a survey of revenue streams, http://www.indignantonline.com/dojo/149/v.jsp?p=/c omics-ecommerce/index was on this board a couple weeks back and is a good overview.

Now specifically looking at your site, you have a little tiny area with google links that I wouldn't have noticed if I hadn't been looking for ads.

You also have the obligatory cafepress/merchandising link buried in your navbar below the fold.

You can't make money if nobody can find your revenue-generating links. Put your advertising in more prominent spots and a little bigger - you can't click what you don't see. Likewise your books and merchandise links need to be higher and stand out more.

Aside from traffic, that's the most immediate problem.