Kerken Kijken met Street View
This Dutch website is the first example I've seen of someone making use of the new 'linksControl' in v3 of the Google Maps API. The linksControl lets map developers add or take away the arrow links in Street View. Kerken Kijken use the arrow links to create seamless links to their own panoramic images.
Kerken Kijken have a number of 360 degree panoramic images of the interiors of churches in Utrecht. They have created this Google Maps mashup to show the location of the panoramas and to integrate them with Street View.
The overall effect is very impressive. As you can see from the sceenshot below the added arrow links to Kerken Kijken's own panoramas are indistinguishable from the links to the adjacent Street Views.