Riot Creative Contest 2017 is a competition by Riot Games and hosted by Polycount that artists, animators and other disciplines can enter. Expect killer prizes, amazing art, and stiff competition.
Cartrdge is a portfolio community for creatives working in video games and is great for creating a page and uploading animations in multiple formats such as Vimeo, Youtube, Gif.. etc
Thinking Animation has a great section on the pros and cons of different rigs. As well as a bunch of other resources and tips across the site.
The Smearframe Slack channel is an animation chat group where you can talk about anything from inspiration, tips, rigs and more. Get an invite from the link above and join the fun!
Newgrounds is a popular website for posting animations, games and audio and has been around for over 20 years. Founded by Tom Fulp (also founder of The Behemoth [game developer])
Animators Resource is a similar website to this one but focuses more on specific posts and videos rather than linking to other websites.
Sketchfab allows you to upload full 3D scenes for others to view directly in their browser. They are the world’s largest platform to publish, share and discover 3D content online and in VR.