Click2Call, provides easy functionality to talk to your website visitors in real time. It has proved to be very effective technique to increase conversions.
This article aims to create list of solutions exists in the market place for Click2Call
Ribbit has a wordpress plugin to add small widget to add to your word press blog.
2. Click to Call Me
These guys have most comprehensive word press plug in available. Very usable.
3. Magic Call Button
Under $10/Month, Magic call button provides Click to call service