Lucid Developer
Photography

Over on Zack Arias photo blog, he runs a series of blog post that critique other peoples online photo portfolios. If you are thinking of putting one together you should go watch a few of them. The advice he puts in is really spot on. From watching them I have gotten a few points:

1. Spelling and grammar will make or break your site and your fledgling business
2. If you don't have it don't show it. In other words if you are going to be a portrait photographer but only have pictures of your kid, get more portraits before creating your portfolio.
3. Site consistency is very important. Don't have completely different looks in your photos or in your galleries.

Please note that I believe what he says, I just don't practice all of it.