There is no other forum like bitcointalk because Satoshi himself was the one who created this forum in order for people to learn and spread the knowledge of bitcoin.

I know of one altcoinstalks forum, but from the name the forum talks more about altcoins without a direct knowledge on a specific coin. In fact, the forum was a mess and lacks good information before forum members here went there to add value to the forum. I believe that if Theymos lift up the ban from mixers, altcoinstalks will become a grave yard with less traffic compared to this present time.