I found this site above that has a story mode for portal. It looks like it has 3 and a half more hours of portaly puzzle goodness. The down side is both small and huge at the same time. No GLaDOS. And as much fun as these might be, ( as I haven't played them yet), They will not be the same without her. They are being released on PS3 and Xbox 360 titled Portal: Still Alive. This explaines it better than I could ever hope to, but in the end. there is more portal, just no more GLaDOS.
Anyway, I'm going to spend some time I should be sending somewhere else on this thingy instead !