Greyhound has a new spinoff called boltbus (boltbus.com). They're operating upgraded buses with free wifi and power points between NYC and DC (presumably other places to follow). The especially good news for cyclists is that bikes go on free, without reservation (subject to space) and don't need to be in a bag.
Worth a look if you're going between NYC and DC and need to take your bike.
Can I take a bicycle or golf bag?
We do allow them and consider them to be oversize items as long as space is available in the baggage area. The oversize item will count as your one bag allowed under the coach. You’ll be responsible for placing the item in the baggage bin. We will not charge you an additional fee for oversized item provided it is within your limit of one bag under the coach. BOLTBUS is not responsible for damage to oversize items or items that are not placed in normal luggage or a carrying case.
Edit: sigh, forgot to put "on new bus service" in the thread title