Street View Maps API v3 Demo
Street View has been added to the Google Maps API v3.
To add a Street View overlay to a API v3 map just add 'streetViewControl: true,' to your map code.
Street View in Maps API v3 uses HTML rather than Flash. The Street View layer in v3 also has the capability of showing your map markers directly in the Street View.
If you open up the demo that I've created and drop Pegman onto Westminster Bridge you can see how the map markers on the map can also be seen from within Street View.