I discovered a company (Brix Networks) that can actually test your broadband connection for VoIP viability. They can measure latency, jitter, packet loss, and even do MOS scoring! Way cool!
Here are some details, with a screenshot below:
TestYourVoIP.com is supported by a VoIP performance management system from Brix Networks. The Brix System consists of distributed test points called Verifiers that communicate with, and are managed by, a centralized server application called BrixWorx.
We installed appliance-based Verifiers, that emulate very-busy, multi-line phones, in the network in both Boston and San Jose. The Java applet on your PC makes a call using the SIP call-signaling protocol to one of these Verifiers. The Verifier answers the call and then measures the quality of the "conversation." BrixWorx assembles all of the test results and provides you with the nifty graphs and tables you see when your test is completed.
Using the unique Brix Tri-Q Analysis, TestYourVoIP.com measures each of the three important quality axes:
Signaling Quality: Call setup performance
Delivery Quality: Call stream performance
Call Quality: Overall voice quality and call experience
Here's a screenshot of my test results on T1 line.