I've set up a complete call center on my computer. I know some great services, software, etc. that can help you out. The software is free. If you just want PC to PC calling, that's free also. If you want to call out to land line, or calls in, I know some very cheap services that work with the software I'm talking about.
Also, I know of one good fax that you can use. If you're sending less than 20 a month, it's free. Other than that it's just $20 dollars.
I can help get you set up quickly. Took me an hour.