I like the way Pentagram displays their portfolio (pentagram.com). It's right there on the home page, interesting design, click a thumb to see more, can filter by category, etc.

It's surprising to me how often design firms (especially smaller ones and freelancers) display their portfolios poorly, probably because they're so busy meeting client deadlines that they don't get around to working on their own sites. (The old "the cobbler's children have no shoes" principle.)