Here is a complete list of all the different themed MOC building challenge months I know about and found in my searches. Each link directs you to its respective Flickr group with discussion topics explaining the fundamentals required to participate if you would like to. If there happens to be any building challenges not on the list then please let me know so it can be added.

1. January: Droneuary, HARDnuary
2. February: FebRovery
3. March: Marchikoma
4. April: FlonApril
5. May: MAYnifigure
6. June: JuneBot
7. July: VehiJuly
8. August: Aughitecture
9. September: SHIPtember
10. October: MaKtober
11. November: NnoVVember
12. December: FOODcember

Well I managed to come across four MOC month challenges to add on the list. I still need the others assuming there are any I don't know about.

I found and added two more month building themes to the list of Droneuary and MaKtober(fest). Droneuary doesn't seem like much of a consistently annual event reading through the Flickr group's discussions however the premise seems intriguingly simple enough. Basically the build is a minifigure scale robotic drone of any size that can range from a tiny mech to a large tank it seems. Only limitations are it cannot be 'ridden' (no cockpit) or controlled by any human pilot like a hardsuit or battle mech. Stuff from Mobile Frame Zero sound like they can fit here far as the build itself is concerned.

Now on Ma.Ktoberfest, I wish there was a simple way of explaining how that works. I understand the core concept on making a build in the style of the universe set forth by the artist Kow Yokoyama called "Maschinen Krieger" which featured lots of war machines kit-bashed from numerous models. It's the consistency as to what defines a build as proper MaKtober material that I find confusing. Well at least there is the For Dummies discussion to hopefully help clear things up and of course Google.

Anyway still six months of building I can't account for. I swore there was something in April or June but don't recall.

A stroke of luck in a search and this list is completed....and it only took two years! Thanks to everybody that helped between....and....then there was....well....never mind. Ah whatever, added to fill in was HARDnuary (common household items), FlonApril (flora & fauna), MAYnifigure (pretty much what it sounds like), JuneBot (mecha), VehiJuly (cars & such), Aughitecture (buildings), FOODcember (....the stuff you eat).

great stuff in those flickr pools.  then may one was my fav

Here is an article explaining what SHIPtember means and how to go about making your own designs towards the event.