Hi,
What iMovie version and operating system version are you using?
The first thing you need to do is move some files off of your computer to free up some space so that iMovie can operate. Running out of space is probably what caused the crash.
Then restart your computer and see if your projects are back.
If the projects still are not displayed, and assuming that you are using iMovie 10.x.x, you can retrieve your projects by going to the iMovie library backups folder located at Go/Home/Library/Containers/com.apple.iMovieApp/Data/Library/Caches/iMovie Backups. When you get there you will see a list of past backups of your iMovie library. Click on the one with the closest date and time to when your system crashed. iMovie will then open in the backed up library. All of your projects should then display.
Another approach would be to restore from your Time Machine backup, or other external drive backup, your iMovie library at a date just before the crash happened.
-- Rich