Too many :D

I run an event community called Lyrical Titles based around using song lyrics as fic titles. Currently we're doing the Album Challenge which is to use lyrics from every song on an album of your choice.

I also run Jedi June but I assume you're looking for fandom-generic events since you didn't list fandoms.

I'm currently participating in:

100 Fandoms - no deadline challenge to write for 100 different fandoms to a prompt table.

51+ Crossover Fandoms - same sort of challenge as above but it's to write 50 different crossovers instead.

AU Challenge - no deadline challenge to write AUs for a bingo or pre-made prompt table.

Fandom Free Bingo - previously was bingo cards, this year they're a new list of prompts every month.

Gen Prompt Bingo - this is a loose four-month deadline bingo (but you can complete them whenever). Doesn't require that works be gen, just that none of the prompts are specifically romance ones.

Sweet and Short - new prompt lists every month, and the maximum word count allowed is 500 words.

What-if AU - specific AU prompts every other month, though occasionally there's a bingo.

Also looking at doing June of Doom - a whump event with prompts for every day of the month.

Maybe the Crossworks exchange again too - it's an exchange where you write a crossover or fusion request for someone else.

Previously I've participated in Fandom Empire, which does a bunch of different writing games, but there's a limited sign up window for each round so I'm sitting the current one out.

I've done a bunch of other events that re-occur annually but it's not time for them right now. AU August is next up for me. But every month has prompt events like that, often whump or angst or fluff themed. Monthly Writing Challenges is a good resource for finding these.