It describes itself as follows:
Collab is a simple, easy to use, free online tool to help bring ideas and skillsets together. If you have an idea and you need to find a person or people to work with you or if you want some feedback on a project you are considering collab is for you.
Posting the ideas to Twitter is a nice touch and allows those who are actively looking for projects to work on to keep an eye on what is being suggested.
If you like Collab, why not help the push and write a blogpost yourself?