Enabling IPv6 on your PC is not as difficult as you think. This is a quick Teredo/Miredo Howto for the most popular operating systems allowing you to penetrate most NATs and Firewalls and most likely allowing you bypass any blocking, censorship happening at your place. As a free bonus, the last link will allow you accessing tons of Usenet posts, including the all time favorite binaries. It does work from China, so you can use it to read your favourite, blocked, sites.

Windows XP
Whatever you do, make sure you have the Windows firewall up, if you use 3rd party, ensure it supports IPv6. Enabling IPv6 will put you on the net, losing any protection you had behind your router's NAT.

Install
Open the Terminal with Start -> Run -> cmd

netsh interface ipv6 install
netsh interface ipv6 set teredo client

Wait for few moments.

Uninstall

netsh interface ipv6 uninstall

Windows Vista
Install
IPV6 is enabled per default. You can get into the settings by going into the preferences for an network interface. "Obtain an IPv6 address automatically" should do the trick. However, Teredo will disable itself if you have "edge traversal" or outgoing udp packets blocked in your firewall or if your router is a symmetric-nat router (e.g. Speedtouch 780). In that case you have to use a tunnel broker, see comments below. If nothing goes, the first place to look would be your Windows firewall... see if there's anything disabled or anything you can enable...
Please leave a comment if you have more info about Teredo on Vista. Everybody I know dumped Vista and installed XP instead.

Uninstall
Add this registry value ("DWORD") set to 0xFF (long line, double-click, and copy):

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\DisabledComponents

Or save the two lines in a .reg file and double-click it:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters]
"DisabledComponents"=dword:000000ff


You can also go to the interface properties of an network interface and deselect the IPv6 protocol for that interface.

Debian, Ubuntu
Install
On Ubuntu IPv6 is enabled per default, but not configured.

sudo apt-get install miredo

Because the default server did not work for me, I had to change it to another one:

sudo vi /etc/miredo.conf
ServerAddress teredo.ipv6.microsoft.com
sudo /etc/init.d/miredo restart

Uninstall

sudo apt-get remove miredo

Fedora, Redhat
Install
About the same as on Ubuntu. On Fedora Core 6 & 7 IPv6 is enabled per default, but not configured. You need to get miredo rpm from the Dries RPM repository.

sudo rpm -Uvh miredo-*.rpm

Uninstall

sudo rpm -e miredo

Mac OS X
Install
Get the Miredo installer from Miredo-Osx, and install it. If you are lucky, that's it. if not, try changing the server, see Debian howto above.

Uninstall
If you want to uninstall, execute the uninstall-miredo.command script, located in the /Applications/Utilities folder.

Checking if everything is working

On the terminal type:

ping6 www.sixxs.net


Getting details about your IPv6 connection

Accessing blocked, censored Websites or just for fun:

http://en.wikipedia.org.sixxs.org/
http://slashdot.org.sixxs.org/

(You can access any Website over ipv6 by appending .sixxs.org to the domain)

"Cool stuff" to do with IPv6 I like the part about Usenet over IPv6