This is a list of every LEGO monthly challenge I could find. If you know of one that is not on my list feel free to let me know by messaging me on Flickr and I will add it. The rules to qualify for this list are as follows,
The challenge needs to last for the entirety of one month. no more, no less.
There can not be prizes for the challenge.
The challenge needs to have a Flickr page where people can post their entries.
The challenge needs to recur every year.