Question : setting up a phone on my internet connection

Hi all
This is a question about running a phone through my internet connection
I have a 10 MB down 6MB up  wireless internet coming into my home and then I have a gigabyte LAN set up internally
Im running a windows server 2003 data center as my DC and have a few PC and laptops all connected to the domain
What I want to do is set up a house phone to run through my internet connection
I dont want any extra costs
All I want to do is get the stuff  needed to set it up ( as cheap as possible )
Get some sort of phone number
And be able to call mobile phones and land lines at no cost per minute
Is this possible?
And if so what are my options

Thanks in advance for any input

Answer : setting up a phone on my internet connection

Look at:
http://www.trixbox.org/

I know it can help you do similar things, you will need to set up and configure a machine to use it, and you might need to buy some special card for sophisticated configurations.