开始使用Asterisk的最佳方法是什么？

I'm interested in learning more about Asterisk (open source PBX) so I thought I would try building a "hobby" system for my home. Just play around with getting a juiced up voicemail system going for my family. That is, until I found out that a TDM11B kit from Digium costs over 0(!) if I want to get an FXO/FXS card with echo cancellation.I'm interested in learning more about Asterisk