Greyhound can be a zoo, but honestly it's cheap and it has always worked for me. Nothing is cheaper, BTW.
For the best results,
Buy your tickets well in advance.
Box your bike with a bike shop bike. Look for a shop that's close to bus station to get the box from. It's possible to fold up the box and ride to the bus station with it, unfold it, and box your bike (use lots of tape).