Go to

-http://bugmenot.com/

and type the URL of the website you want to log into.
Examples:

-http://www.nytimes.com/, -http://www.winnetmag.com/
etcetera.

Another (and better) way is changing the user agent of your browser to:
Googlebot/2.1+

-http://www.googlebot.com/bot.html

This is very easy in Mozilla's Firefox. Download and install the User Agent Switcher from

-http://www.chrispederick.com/work/firefox/useragentswitcher/
and add the Googlebot user agent.

Have fun, Dead Dreamer!

-]Edit[- Now this kicks ass, was just browsing entire forum without even needing to login to view restricted areas, and it works on other sites
And no, you cant access the hidden forums either, already tried that