In case you might be in the USA (since your profile doesn't give your location)...
I've shipped large items (not necessarily bikes) via Greyhound and got good bang for the buck. The catch is that the recipient needs to pick up the item from a Greyhound bus station.
It's been a while, so I don't know if the service has changed, or how pricing compares to a service like BikeFlights. You can check it out at
www.shipgreyhound.com .