Recently launched Google Voice is excellent service for U.S users. However in order to receive messages you have to keep Google Voice webpage open this may be inconvenient many & you may close it mistakenly.
To make it easier for you stay connected with your Google Voice account here is very useful Adobe AIR based utility GVoice. GVoice – Google Voice Utility helps you keep Google Voice open on the desktop and it can work on Windows, Linux & Mac. GVoice is still under development and it may contain bugs.