The actual bugdet for the NSA I believe is classified. However, you are looking at an agency whose bugdet (as well as manpower far outnumbers the CIA). I think we are talking billions and billions here.
Addendum:
The prior answer is correct. I would add only that it is believed that the NSA budget is the largest for any single agency.
Second Addendum:
Largest intelligence agency by budget is National Reconnaissance office, due to size of space missions, not personnel or ground facilities. It is approximately $15 billion per year. NSA is roughly $10 to $12 billion per year, counting Central Security Service.