[dotpavan]

You can- 1) If you initiate a call via browser from GC's site, you have the option of making the number of your choice (your GC or cell/land #) or 2) if you use GrandDialler app on iPhone, it too can make the call with your GC # as the source

edit- forgot to add, there is vocito app (http://code.google.com/p/vocito/) for mac

[rufo]

In addition, there's now an option when you dial your Google Voice number to just dial directly - the "Place Calls" video at https://www.google.com/voice/about demos it.