I bought a SkyLAb GPS from ebay (under $30 w shipping)
For an inexpensive device it works pretty good
The HDOP is in the 100 meter category and the number of sats is typically 7 to 10
but it does work even in the house if it is within a few feet of a window.
the TinyGPS library and examples work just fine
it is fairly slow, specs say 1 Hz but it keeps up in the car at 55 mph
I don't think it would work very well in robot or quadcopter --too slow and not precise enough
but for a lot of routine projects it is a lot of nav for the buck IMO