Free IPv6 tunnelbrokers

A tunnelbroker is a service that gives you access to the IPv6 Internet by encapsulating packets inside IPv4 ones and tunneling them between two points, somewhat similar to a VPN (but providing neither authentication nor encryption). The following tunnelbrokers use 6in4: protocol 41 encapsulation and static tunnels.

https://tunnelbroker.net/ - from Hurricane Electric. Gives you a /64 prefix out of the box and /48 upon request. Relays all over the world. Requires a pingable IPv4 address to set up the tunnel. Dynamic updates are supported.
https://tb.ip4market.ru/ - from IP4market. Gives you a /48 prefix. Relay in Russia. Asks for a phone number upon registration, but doesn't use it for anything. Dynamic updates are supported.
https://tb.netassist.ua/ - from NetAssist. Gives you a /48 prefix. Relay in Ukraine. Dynamic updates are supported.

You can calculate how many addresses will be available to you with the formula 2^(128-x) where 'x' is the prefix size. The usual practice is to assign one /48 per customer, and let them divide in smaller /64 subnets as they please.

Anyway, I have tested all of these and they worked fine. Setup is easy and only involves running a few commands, but additional help is available if required. The only downside was high latency as a result of not having any relays close enough to my country. If you set up the tunnel in your router, you can have everything in your LAN receive IPv6 addresses from your allocated prefix transparently. In practice, this may be the only way to achieve that for more than one computer or at all, since 6in4 and NAT don't work well together. OpenWrt in particular has built-in tunnelbroker.net support, which solves the problem of having to reconfigure the tunnel whenever your external IPv4 address changes.