IOTA Slack, one of the biggest and most informative; not too many trolls either. (10,739 members on July 9th, 2017)
IOTA WikiCool IOTA Nodes site with a bundle of IOTA links Cool Blox Tangle Visualizer IOTA ledger, check the confirmation times here David Sønstebø, the Founder of IOTA on Medium. If you want to learn and understand IOTA, and follow what’s new, go there
IOTA’s AMA (“Ask Us Anything”) on Reddit
Tangleblog’s YouTube channel devoted to IOTA is here.