I was in the CAP for bit, got about 13 hours dual in a 172, room/board (for a week), ground school, and the Gleim Private Pilot books, all for about $500. You had to interview to get in, as spaces were limited. It was meant to get you to your solo (or close to it), and basically act as a jump-start to your flight training.
Aside from that they did (and believe they still do) have "Oreintation" flights where you go up in one the planes and fly around (all free). Aside from that you can get instruction in one of the aircraft (not sure if that changed or not) and only had to pay for cost of operating the plane. They also offer a bunch of scholarships to help pay for flight training, and college.
The cadets and senior members both conduct search and rescue, the cadets are restricted to the ground part of the search and rescue. They have camps to go to which train cadets and senior members in how to conduct these searches. They also help out in diaster relief.
Aside from that I think the senior members also help out in drug enforcement, by flying around and looking for marijuana fields and stuff like that.
Some people were really into it and acted like they were in the military, others were pretty cool about it. Its a mixed bag, but all in all they were a pretty good bunch when I was there.