GizmoCall - a service provided by Gizmo Project now lets you make free calls to any phone (limited to 5 minutes per day if you’re an unregistered user) right from your browser! I’ve just tried to make a simple call to my own handphone and it seems to work nicely… 
Just some heads up, although it says that you can call directly from your browser; there are a few requirements before you can actually do that - you’ll need :
1. A Windows (2000/XP) or Mac (OS 10.3.9+) computer
2. A headset, or speakers and a microphone
3. A web browser with Adobe Flash Player 9 installed
4. Install the Gizmo Call Plugin.
Once you’ve got that sorted out, just point your browser to GizmoCall.com and start calling!
Check out their FAQ for more info. 
Now, who should I prank call next? hehehe…
Cheers~!
