There are many good options discussed on the forums. I'm using Callcentric as a backup and like their service, but have been using Vestalink since it was announced and haven't looked back. All the added features are a perk, but the appeal to me was simple and easy phone service at a low price as an infrequent landline user with cell as the primary phone. For a fraction of what I was paying Comcast, I've experienced better service and call quality. Others have had varying experiences, but I had similar need to what you describe.