I'm an accademic, so I wear two hats: researcher and teacher (i.e. creating knowledge and sharing it). As a teacher, I try to present material in a way that's interesting, logical, and most likely to be absorbed by my audience. Most of my peers try to do likewise.
However, when I go to conferences or seminars, it seems like my tribe (the clan of pointy-headed nerds) throws everything we know about effective presenting out the window. The first rule of conference presentations seems to be "suck all the life out of your presentation". The second is, "use busy tables with lots of 10-point type".
Here's a nice post on using PowerPoint from Working Smart titled Five Rules For PowerPoint Presentations. It's geared more towards business presentations than to academic ones, but the principles are the same - it's only the implementation that changes.
It also has links to some very nice resources.