This is a thread for game jams.
I found a few you might be interested in. These are all now running or will start very soon. As of January 3rd 2018 they all offer a decent amount of time to complete:
Finally Finish Something 2018 (yes, let's be finishers!)
There are way more jams going on out there than just these. I posted a few that offer a few more weeks to complete, and have at least 30 people signed up for already (these more popular jams will get more eyeballs on your project).
Please feel free to add any more jams to this thread.