I’m a member of Holly’s Writing Classes, and the forum on the same website. This is one of the more stable writers’ groups I’ve found on the internet, and well worth the investment in time and money.
I’m also a founder and participant in the Story Time Blog Hop, an internet get-together and show off of sci-fi and fantasy writer’s that’s been going strong since 2015. The stories here aren’t necessarily intended for children, but we keep the “rating” around PG.
Founded by Alex J. Cavanaugh in 2011, the Insecure Writer’s Support Group is a great place to meet other writers, and bemoan the pitiful size of your coffee pot.
They We post monthly, and signup is here: http://www.insecurewriterssupportgroup.com/p/iwsg-sign-up.html If you don’t have any insecurities, one will be provided for you in the form of a question.
The A-to-Z Blogging challenge is a great way to get into blogging regularly. During the month of April, you blog your way through the alphabet.
And what list of writing communities would be complete without NaNoWriMo and Camp NaNoWriMo? The program is a little hit-or-miss, depending on where I am in my own creative cycle, but the forums can’t be beat, and I always meet some amazing people.