I'm sure there are more than a few ways but I know of Google Voice being great for recording calls, conference calls etc but you have to manually make it record each conversation. Some seem to think it only records outgoing calls but others say if you set it up right it records everything.....
Read here to learn more.
Other apps, if you haven't tried them, are:
AllCallRecorder
Calls Log (Secret Monitor)
I found this information by googling