Voice over Internet Protocol (VoIP) communications are an excellent, inexpensive way of staying in touch with friends, family and contacts via the Net. There are a huge number of applications and accessories out there to connect to VoIP services, but many of them offer limited (or a complete lack of) support for Mac users.
The guys at VoIP Now have put together a mammoth guide to the very best VoIP tools for Macs, plus some pretty useful security advice, considering how much hacking is going on these days.