Asterisk is a great Open Source Phone System that can give you a lot of great features (including T1 integration and VoiceMail) at a fraction of the cost of a proprietary systems because all of the Asterisk software and hardware are based on Open Standards. Open hardware and software solutions give you the best value because Open Systems based on Open Standards create competition between hardware and software vendors providing you the best possible telephony product and support solution at the best possible price. For example, the Aastra phones have twice the features (including backlit displays) at half the cost of proprietary phones.
Asterisk Appliance -- Full-featured, Cost-effective Internet Telephony in a User-friendly Package for two to fifty users, includes firewall, PBX, voice mail, router with Business level support
Ekiga Softphone for Linux -- Ekiga comes built-in to Ubuntu; Ekiga is a SIP and H.323 VOIP phone that runs on a Linux system and can speak to any SIP or H.323 based IP based phone system Asterisk).
Using Asterisk to listen to Podcasts. Also seems like you could dial into audio podcasts this way as well. Combine this with the voice menu, and you can provide a structured interface to podcasts, both live, and pre-recorded.