Make free calls from this web page to anywhere in the USA ... while a computer analyzes your conveersation and pops up web pages, news, images (*ahem*: advertisements) on the web page which are "relevant to your conversation" ... Free, but with a price.
"The goal of this project is to bring programmatic control of Google Voice to Java Developers. This includes Placing Calls, Sending SMS messages, and viewing Inbox, Voicemails etc. Developers are welcome to contribute to this Open Source project. "