JetBlue, which is how I'm going to get from Chicago to DC for my Philadelphia trip this summer, has an awesome checked baggage policy.

Free Baggage Allowance

• You may bring two bags per person free of charge.
  
• Each bag must not exceed 62 inches in overall dimensions (length plus width
  plus height) and can not exceed 50 pounds.
  

Sporting equipment which does not carry a service charge may be substituted
for the free baggage allowance. Sporting equipment such as surfboards, windsurfing
equipment, and bicycles are exempt from oversize fees.

So, if I'm reading this correctly, I can just pack my bike and use that as my checked baggage allowance! And I think it counts as only one thing so I can still take on a suitcase as well. When I finally order my ticket I'm going to give them a call and ask exactly what's up with that but basically no matter what I don't have to pay to take my bike on the plane