I do this quite often...they way I handle it is to use my
GrandCentral: The New Way to Use Your Phones account. Among other very handy features, grandcentral has a record feature that works quite well. At the conclusion of the call, it will email you the recording as an mp3. If you go this route, however, you either need to have the caller dial your grandcentral number or, if you are initiating the call, you need to use the utility on GC's site to connect the call.