Is this fringey Halogen tweed too funky? I'd wear it for this kind of thing (with black trousers and a shell, maybe) , but I have a bit of that whole academic-wanting-to-poke-the-doctors thing going on. =P Might be moot, though, as it looks like it's sold out in most sizes.
The floral blazer (not NAS, not available) is something I own that I'd wear for this kind of talk. With dress pants or plain dress for a medical-type conference, and with jeans for a scientific one.
Definitely do some funky shoes.
ETA: Gretchen makes a good point about the mic and battery pack. The latter makes it tricky to do a dress unless it has a substantial pocket to clip the pack onto. Pants pocket, belt, or even waistband in a pinch is almost always OK. If you wear a jacket, you won't have to worry about the mic - you can always clip it to the lapel. But a top or dress w/ a lower neckline can be awkward.