Double Dawg Dare was the big one that I recall; pulled my dormant '67 Galaxie out of mothballs to go to the finish, or, finished enough for the pictures. (I may go back for a Mk. 1.5 chassis resto, have some better ideas for how to handle a few things...)
Curbsider's Ball was another that I had a blast chasing down, the pics of the Rambler stawag are someplace deep in a hard drive.
Others that felt a little more ordinary like Same Subject, etc. got okay response, but not really strong traffic builds.
To the point of the OP, the pendantic, passive-agressive whining of a few bad apples in the 00's caused many outstanding contributors to leave here for FB or MCM, where most circulate today.
Hoping that the change in the board's programming to allow drag and drop photo posting will recharge the WIP / How-To vibe, here, which was the great feature of the "message board" early on and has fallen off dramatically save for a few contributors.