For security stuff, only Malwaretips. This is the most user-friendly and nicest community, so I hang out here most of the time.
For other IT related stuff, not necessarily security, I also like:
My Digital Life
I used to like Wilders a lot, and even still have an account there (that's banned from posting, but still). Highly knowledgeable members actually, but I now find them too draconian and controlling. Most of them also look down on anyone but AVC or AVT reviewing AVs, considering these tests "self aggrandizing" and "unscientific" even if it's unwarranted. I'll agree that most of everything is mediocre or bad, and these two testing organizations have the resources the others lack, but very large sample sizes can also be a disadvantage in that you can only test products based on a very limited set of criteria. This forum is also a lot more helpful and interactive.
Back then I also visited Rokop Security every now and then to read people (both apologists and critics) ranting about G Data. No offense to the Germans and/or anyone who likes the product, but most of what I've read in various sites on the net painted a very negative picture of G Data including insularity, provincialism, inept support, penchant for slowing down or even trashing computers, inability to detect threats, and worst of all, putting their image before actually improving the product (emphasis on the "Made in Germany" cliché, pulling off of AVC due to doing badly in zero-day tests, the "Germansicherheit" hashtag on Twitter etc) - basically filling the vacuum left by the old Norton/McAfee.