It looks like my old colleague, Jeffrey McManus, has been busy with his counterparts on the Yahoo! Messenger team to launch a Messenger plugin framework. One amazing plugin (yes, I'm biased) is for eBay and allows you to monitor your bidding and watching activity using the eBay API.

Although this is cool, I still love Skype (again, I may be biased) for the call quality and third party extensions through Skype's developer network. For example, I now use the Polycom speakerphone for Skype and love it. Hats off to the Polycom and Skype guys on building a great product.