I think you will have heard of these 3, but you should definitely check out the following:

1. https://experiments.withgoogle.com/ai
   A showcase of different AI projects, most of them have demos which allows you to get a feel for what is going on in the AI space

2. http://steem.supply/
   The best reward calculator for STEEM, at least out of all of the ones I've seen

3. https://Utopian.io
   I would hope everyone knows what this it, but a great site for contributing to the Steem blockchain and as you'll be able to see from my post one I use regularly