Modernista delivers one of the most unexpected agency portfolios by using UGC tools to display their content. Their site is sort of an un-site. Once you arrive at their domain, a smallish red navigation widget that's 50px x 80px displays in the upper left of the screen. The rest of the screen is taken over by an 100% x 100% iframe showing their Wikipedia page.
For the most part, the red widget is the only bit of the Modernista identity you see in their experience. The navigation contains fly-out menus to branch out from the primary links, and each link in their navigation loads a web page hosted on an external site. About displays Wikipedia, Facebook, and links to bookmarking services. Work displays their portfolio photos in Flickr, and their video in YouTube. News displays articles about Modernista in Google News. Contact displays their addresses in Google Maps. The only destination page that appears to actually be hosted on their servers is their jobs search interface.
This is really a different way to deliver a portfolio, and is sure to make heads turn. Putting your trust in other sites to deliver your message is, in my opinion, a bit of a scary proposition, however.