I feel bad just coming here to post a link, but another great resource is Mark Boulton's "Designing for the Web". It's been released as a free book online[1]. (I'm not affiliated with this in any way)

It has lots of detail on typography, but focussed around the web. It also covers things like colour and layout amongst other topics (e.g. research and workflow, which I find less insightful). It's a great and fairly quick read :)

[1]http://designingfortheweb.co.uk/book/index.php