A client of mine asked me to start using Skype for phone calls about a month ago, and it's great. First of all, it's free to conduct voice, video, and/or text chat sessions with other Skype users. It's also free to use Skype to call any home or mobile number in the US or Canada until the end of this year. And it works.

I don't have a home phone, and a few months ago my cell phone bill was sky high because of a spike in long business calls I had to make. Skype has already saved me money on my cellular bill. Granted, I can only place calls for free - accepting calls requires a SkypeIn account (currently running 30 Euros, or around $38 USD for one year) - but I can always field a client call and call them right back from Skype. Skype Voicemail is also available for 15 Euro ($24 USD) a year so you can send voicemails to people when they're not logged into Skype and they can do the same to you. Skype SMS also allows for voicemail-esque delivery of text messages to other Skypers when they're offline for 9 cents a pop in the US (International rates vary).

Skype also has a nice text chat interface that allows for an IM-like experience within the application. I've used this to great effect with clients and colleagues, combining voice conversations with text messaging of URLs, written copy, data, file transfers, and so on. In this way, Skype functions like iChat AV. An OS X beta of Skype 2.0 supports video chat, as well, with fairly solid results (Skype for Windows already officially supports video). Additionally, Skype is starting to preview and promote Skypecasts (a cross between podcasts and party lines on specific subjects) and SkypeZones (pay Skype-specific public hotspots around the world; SkypeZones are not yet OS X compatible).

The Skype interface is simple, clean, and attractive. More importantly, the voice quality is excellent. Some kind of microphone and speaker is obviously necessary to make voice calls, but you really need at least a pair of headphones to avoid an echo effect caused when your call is amplified through speakers and then that amplification is picked back up by the microphone. I've used Skype with my iBook's built-in Mic and a standard pair of stereo headphones and it works just fine. Wireless headsets and those with built-in mics will, of course, yield better results.

Skype-specific accessories are starting to hit the market, including USB and Bluetooth headsets and Skype phones that connect directly to WiFi networks. In addition to the OS X and (of course) Windows versions of Skype, Linux and PocketPC versions are also available, the latter of which is starting to come pre-installed on WiFi-capable cell phones. In short, Skype is one of a few VoIP providers leading the Internet telephony charge. Check it out, especially while it's still free to call your "old school phone" friends.

Skype 1.5 and 2.0 (beta) for OS X are free and available for download from the Skype Website. Outgoing calls to mobile and landline phones in the US and Canada are free through the end of 2006. Incoming calls and other services are available on a paid basis - check the Skype website for rates and details.