[FateOfNations]

Big evil Comcast gives out a /60 to residential customers if you ask for it (via setting a DHCP option). That allows for 16 networks to work with.

[akira2501]

DHCPv6 Prefix Delegation. If you're a business customer, you get a larger allocation seemingly depending on the size of your IPv4 static block. I've been given /56 and /54 from their business service. It's quite nice.