The issue, at least for me, appears to be with Comcast. I've confirmed that Google is accessible on both Verizon and T-Mobile networks.
Since I happen to be working on a web application with several scripts pulling from Google's CDN, I needed access to it. Assuming you have a server that is not on Comcast's, you should be able to setup a simple SOCKS proxy and tunnel your traffic through it:
ssh -D localhost:6772 username@hostname
Assuming OS X as your OS, go under Network Preferences -> Advanced -> Proxies, check "SOCKS Proxy" and enter the host/port.
From there, your internet traffic should be tunneled through the server.
