I take it you bought your tickets in the US. If this is the case, write a registered letter to Aer Lingus and tell them you plan to sue if compensation does not come within two weeks.
Gather all the material you have at hand (ticket copies, schedule, CC receipts, EU decision in regards to compensation and send all of it to your small claims court. I see you are from DC, here is the link as to how you have to proceed.
Good luck and let us know how it went.
http://www.consumeraffairs.com/consu.../small_dc.html