Ask any geek: Asterisk is the new hotness. The open source voice-over-IP software is revolutionizing the world of Private Branch Exchanges, or PBXs. You’ve used a PBX before, even if you don’t know what it is: every time you dial into an company’s call-receiving system and navigate a series of menus through the use of your phone’s keys, you’re working within a PBX system. The same goes for when you check your voicemail at the office, or route a phone call to an extension one meeting room over.

PBXs used to be implemented via expensive hardware from unapproachable vendors. Asterisk is changing that. You can install the software on even a modestly specced machine, subscribe to an inexpensive VoIP provider like BroadVoice and be routing calls in no time — and doing it between a variety of data streams. Asterisk allows VoIP, SMS, fax, the Plain Old Telephone System and the internet to be stitched together with relative ease. It’s not exactly user-friendly (although there are GUIs that make it a bit less hostile), but it’s not rocket science either.

The real trick comes in knowing what to do with Asterisk, not how to do it. There’s plenty of money to be saved by companies looking to roll their own office voicemail systems or create more efficient means for routing customers’ calls. But that's a little boring. For the stuff we get excited about, Asterisk’s role is still being defined.

I started directionlessly playing around with an Asterisk install not too long ago. You can hear the results by dialing into 202-318-0196 (for a while, at least). Once there you ought to hear a greeting and be prompted to select one of our ten most recent podcasts, thanks to some basic Perl and Asterisk’s AGI interface. Press a button and you’ll be able to listen to the selected podcast, unchained from the tyranny of traditional MP3-playing devices. Hurrah!

I’ll be the first to admit that this particular app is kind of stupid — and to offer my apologies for the poor quality of the computer-generated title-readings. Nobody really needs a crappier, more expensive way to listen to podcasts. This effort resides strictly in science-project-land, and as a result I haven’t put much time into making sure everything runs as well as it would for a production-quality system (if I have a big download going on my LAN, your connection might suffer, for instance). Interested geeks are welcome to a look at my scripts' source. The podcast-grabber runs on a cron and can be found here. The actual Asterisk AGI call script that plays the files and responds to your keypresses is here.

To be honest, I don’t believe there’s a tremendous amount to be gained by mashing Asterisk together with podcasting tools. Odeo’s efforts on this front are neat, but ultimately a bit pointless – the portion of podcasters with worthwhile content but no drive to figure out how to record it properly is probably pretty small. POTS-to-mp3 may be useful in some situations, but using Asterisk to do it is overkill; Skypecasting fits the bill just as well.

In large part, I think the killer advocacy apps that use VoIP have yet to be dreamed up — but it's not hard to do so. Flash-based audio shoutboxes would be a trivial but neat addition to community sites. Automated, prescheduled conference calls could help online community members find one another at IRL events like rallies or meetups. You could even whip up a distributed phonebank application without too much trouble. There are a lot of ways to take advantage of the immediacy and accessibility of a cell phone.

Every day it’s becoming easier to stitch together the various information services that we consume. Asterisk is poised to be the glue that brings phone service into the online arsenal.