Yeah, I searched through all the Google Fonts to try to find a good serif font but they all seemed either too light or too heavy, so ended up just using Garamond and URW Palladio L - the Garamond was a bit light but I kind of got used to it.
There is a free alternative called ET Book though, which looks better - it would require hosting on the EmacsWiki server or a CDN. I'll push it up to GitHub if anyone would like to try it -
http://www.emacswiki.org/emacs?action=""> - reset with http://www.emacswiki.org/emacs?action="">.