The creation of better resources for online communication and collaboration. There is so much that can be done here.

Google wave was fantastic it was a shame it was killed. Rizzoma improved this concept by adding todos and the ability to tag people, but unfortunately their interface was still clunky and had performance issues.

Stackoverflow revolutionised the question and answer model for programming, but open source clones appear to be far inferior, and so creating one of these sites is subject to a single gatekeeper.

The mailing list and forum models have had long periods of stagnation. Recently, Groups.io and Discourse demonstrated that there was value in modernising these tools. This demonstrates that it is worth taking another look at these tools to see what can be done with them.