Plex Recorder is a free to try tool that works in conjunction with Skype for recording calls. It has the following advantages: can work in automatic or manual mode, automatically compressing to MP3/WMA formats, can save recordings as WAV PCM format, records conversations either in single or dual audio track, can work with PC-to-PC, PC-to-phone as well as Skypecast conversations, all versions of Skype supported, doesn't inform other side that you are recording the conversation, user-friendly interface, etc.