VoIP for SMB/SOHO

I have various clients that are looking for advice on what would be a good VoIP solution for them. They are specifically looking at getting rid of the local telecom (SBC) and their constantly rising prices.

I specifically have one small company that wants to get VoIP set up so that he can sit at the local coffee shop talking on his PC-to-phone, etc… He is also wanting to replace his dedicated phone line for his fax machine as well, since this would drop his monthly line fee from ~$32 to ~$16.

I’m rather leery about his, however, looking for any advice at all.