Here's a site with lots of info about using the phone lines.
**broken link removed**
I wrote this January of 2004. It was meant to mostly discuss using modems, but if you get the isolator circuit mentioned, you can introduce audio devices (speech chips, modems, tape recorders, etc.) as well. It was designed specifically fo rusing a PIC driven circuit, but there are bare essentials in this tohelp in many ways.
Whatever you do, DO NOT just connect a cap and resistor to the phone lines. Besides being dangerous, it's illegal. You'll understand when you get to the part about jail time and stiff fines.
Hope you find this helpful,
kenjj