Assessment tools

You can use these LMS/assessment tools as a platform to run your online hackathon. 
Please refer to the Complete Host Book for (much) more details on how to run an online hackathon! 

ClassMarker (freemium)
Quizzlet (free)

PeerWise (free, but you need to be part of a university that is implicated in the project) 

CoboCards (free)

GoSoapBox (free up to 30 participants if you're an educator/teacher)