You're right about much of Google's imagery being aerial. I know for a fact that the NJ imagery is the latest USGS orthophotography.
The highest resolution commercially available satellite imagery is from GeoEye (GEOY). The GeoEye-1 satellite was launched three years ago with .41m/pixel panchromatic and 1.65m/pixel spectral sensors. They combine these to produce .5m resolution color imagery. Earlier standard was the Ikonos satellite with 1m resolution. Check it out.
http://www.geoeye.com
This is a .5m image of Vatican City from GeoEye-1:
