Algorithm Visualizer - Write down your algorithm to be visualized
Slackbot Workout - A slackbot to get your team in shape
Algorithmia - Algorithmia makes applications smarter, by building a community around algorithm development, where state of the art algorithms are always live and accessible to anyone.
Quantiacs - Earn money by creating trading algorithms in your spare time
Grokking Algorithms - An illustrated guide for programmers & other curious people
Breaking Equity - Algo trading platform for retail investors