Asterisk is the world's leading open source PBXi, telephony engine, and telephony applications toolkit. Offering flexibility unheard of in the world of proprietary communications, Asterisk empowers developers and integrators to create advanced communication solutions...for free.

Anyone played with it before? Wouldn't mind hearing your thoughts about using it in the small business environment??

http://www.asterisk.org/

I played a couple of years ago and it did everything it said would. It did take some setting up but as it was my first attempt and I was guided by fan sites because the docs were not that flash back then everything worked.
I had a company in mind to adopt it in place of their regular PABX but like all best made plans that never eventuated and I moved on from being a sole trader to being a slave to "the man".

Regards