Where can I listen to the actual cockpit voice recorder audio from US Airways Flight 1549?
You can't, because it is in fact forbidden to release CVR audio under US law. From the NTSB:


  The CVR recordings are treated differently than the other factual information obtained in an accident investigation. Due to the highly sensitive nature of the verbal communications inside the cockpit, Congress has required that the Safety Board not release any part of a CVR audio recording.


Other countries may have different rules.

This rule came about after the crash of Delta Air Lines flight 1141, (commented by @MichaelK)


  [...] where the crew — in extremely cruel irony — were bantering on the flight deck about what to say that would get captured on the CVR in case of a crash. That irony was then squared in that the bantering was a directly contributing cause of the crash, in that they forgot to deploy flaps and slats