There is still no specific website dedicated exclusively to round the world tours, apart from this one!
But you can try discussion boards such as virtualtourist.com and lonelyplanet.com Thorn Tree, where you can post and read messages on specific travel topics. Travel blogs are another source of first hand advice and information.

Bootsnall: A large community for ‘indipendent’ travelers.bootsnall.com

Round the World Travel Guide  by Marc Brosius. Very useful for finding out how other people have dealt with some of the logistical, practical, and other issues of around the world tours. perpetualtravel.com/rtw/

Real Travel: Travel blogs, useful to find out what other people did, what they liked or not. You can search by destination, activity etc… realtravel.com

IgoUgo: Real people sharing travel experiences. igougo.com
Tourism Office Worldwide Directory: useful to find government tourist information offices (especially in the USA) towd.com