Here are a few other online fora hosting miRNA discussions.

BioForum siRNA, microRNA and RNAi discussion group
http://www.protocol-online.org/forums/index.php?showforum=21

Scientist Solutions miRNA/siRNA discussion group
http://www.scientistsolutions.com/f508-miRNA_siRNA.html

Molecular Station’s RNAi and siRNA forum
http://www.molecularstation.com/forum/rnai-sirna-forum/

Gene Tools board: blocking miRNA with Morpholinos
http://p196.ezboard.com/fmorpholinosfrm24