What is a absolutly free voip service for pc to phone with no catch or time limit?

I am having a really hard time finding an absolutly free voip service for pc to phone. Most of them cost or have catches can someone point me in the right direction.

Related posts:

1. How to make international telephone calls to India using voip service, is there any provider for free service?
2. How to make international telephone calls to Inida using voip service, is there any provider for free service?
3. Is there any VoIP service that has free incoming and outgoing SMS messages?
4. Unleashing The Facts About VoIP Phone Service
5. I want to use vonage voip, so do I still need to keep basic att phone service to keep the dsl line?