You can get a bunch of /64s and a /48 for free because HE really wants everyone to have IPv6 available already. Picking the right internet exchange to route from and making Netflix not throw a fit requires some minor experimentation but I've found it to work quite well.
As an added bonus, because of the way IPv6 route advertisements work, you don't have to have a router with tunneling support. You can set up advertisements from any Raspberry Pi or other computer as long as it has outbound connectivity.
None of the 4 VoIP providers I've worked with support IPv6 :-/
You mean send the advertisement and do the SIT tunneling on that machine?
You use one of the /64 tunnels provided for you to route the /48 tunnel to the rest of your network. You advertise a subnet from your /48 to your local network and if you've got SLAAC enabled on your hosts that's all there is to it.
You may need to mess with the default DNS server to get IPv6 results, though, that depends on whether or not your standard DNS server will respond to AAAA requests. It usually should, but some ISPs don't.
This only works for a flat network, of course. If you've got different routers, you'll need to set up a more complicated setup.