Hi Mike,
There is a plugin which would allow you to assign a (web) URL to any entity in SU - say a building that's turned into a group and such. You need to right click though and select the URL item in the context menu and then it will open a "normal" browser window, not a neat, chromeless one within SU. (see url_link.rb here)
There were requests for this during development of SU 7 though because (theoretically) dynamic components could do this but AFAIK Google finally didn't include this feature for security reasons. I see you have SU 6 anyway so you couldn't go anywhere with DC's as it needs SU 7.
I'm pretty sure however that with some modification of the URL plugin, it could be made nicer in SU because webdialogs have been implemented since that script was written (before SU 6).
OR you do the whole presentation in Google Earth and add as much rich html content on click as you want.