Rick Steve's website has a place for solo travellers to inquire about travelling companions.
http://www.ricksteves.com/graffiti/graffiti14.html
He also has some great tour options.
I'm with Tom though, you're never really alone when you're travelling. Especially if you're a budget traveller, and even more so if you're an FT'er.
Finding a compatible travel companion is truly a gift though...good luck!