This great list of National Poetry Month online open mics and readings curated by Devi Lockwood includes a list of online open mics, readings, classes, workshops, and prompts. I’m specifically watching for the next Self-ish open mic, and you can imagine why :). Also on the list, one of my favorites hosted by Kai Coggin, Wednesday Night Poetry, such welcoming and well-organized events! There are some excellent readings also listed by Copper Canyon Press, Poetry is Bread, etc.
For more National Poetry Month resources, check out my my post: April is National Poetry Month! #NaPoMo–Prompts galore & other ways you can participate.