I was looking at other websites for poster presentations. I found some good ones.
Design of Scientific Posters
This one has some good samples.
This website has lots of links for readings and instructions.
The most interesting thing, though, is that it also has links to sample poster sessions online. I think it would be interesting, when teaching poster design, to have the students go to these and create critiques.
Advice on Designing Scientific Posters
He has a good introduction, with good visuals, to what it means to be presenting a poster presentation.