VOIP Recorder is desktop software (available for Windows, Mac, and Linux) that records normal Vonage calls without any special configuration. Just run it on the same LAN as your Vonage ATA and VR will redirect the VOIP calls through your dekstop where it can make a copy. Playback and archive management is through an embedded web interface.
Read all about it and register for a free download at http://www.penbaynetworks.com/
VR has other features too: pop-ups with Caller-ID info, optional insertion of announcements, touch-tone based triggers, Caller-ID based call blocking, voicemail tracking, and more.
An Example Caller-ID Popup