http://www.lettercount.com/

The page doesn’t look very good, but it does a good job. It’s a simple task, but sometimes can be annoyingly time consuming if you have to do it manually.

Smashing Magazine came up with a nice short list of tips to improve typography for your site: 8 Simple Ways to Improve Typography In Your Designs.

This could improve the user experience for your site dramatically, particularly if your site is text heavy.