Metadata and microformats
<shamelessPlug>I happened to notice earlier on (OK, I admit it... I was checking at the time) that my Does metadata matter? slidecast has been featured on the Slideshare homepage.</shamelessPlug> In doing do, I also spotted a similarly featured presentation called What Brian Cant Never Taught You About Metadata by Drew McLellan - such a great title that I couldn't possibly ignore it!
Turns out to be quite good, though much of it is about microformats (which isn't hinted at by the title).
Don't know what microformats are? Try watching Drew's 5 minute Clangers' Guide to Microformats.