I found this post referenced in the Boagworld podcast, and I have to say it's just a must for anyone involved in website design and development. No matter how well you know CSS, or how little you work with it for that matter - this has some really great insight and advice. Very well written and documented. Natalie Downe, of Clearleft gave this presentation at BarCamp London 5. This post gives a link to a PDF of her presentation complete with all her notes - essentially like sitting there hearing her give the whole thing (or so it seems - I wasn't there... but loved the read).
Natalie Down's talk on CSS Systems (essentially an anatomy of a well-architected CSS implementation)