I am a big fan of Smashing Magazine, an online design resource for graphic and web designers. They always have interesting articles that help in all aspects of design. They also have lots of freebies like fonts and tutorials.
Recently released is an article called Typographic Design Patterns and Best Practices which I found of particular interest. The team did a survey of the top 20 websites to compare things like font styles. font sizes, background colours.
What I found of most interest is that the most popular size for fonts was at 13px and the most popular font-style for body font was Georgia. A long way from when the standard web font was Verdana 10px.
A really interesting article with plenty to think about.