Marketplace
12 months of humble monthly, starts with this month. Not targetted in any way, you can access it from the site directly.
Also:
Also, it's worth saying that you don't technically get a year, back-to-back - you get 12 monthly "credits" instead. So if you don't like a particular early unlock, you could choose to "pause a month" and not use one of your credits for that month, saving them for later. You need to actively choose to do this, but you can do this as many times as you like.
(Courtesy of /u/zellisgoatbond on r/gamedeals)
The last few months haven't exactly been inspiring, just 2 poor months over 12 and that $20 would be worthless compared to spending $12 whenever a good month turns up. If you look back over the past 12 months of games and see multiple months where you wouldn't buy that month, signing up to a year isn't worth it.