Levelless Cleric system? This is brilliant. Definitely a niche that needs to be filled. There's a lot of levelless wizard stuff out there, but I haven't seen much for clerics.
This was an instant buy for me.
Good question! I don't have a ton of experience, but I've encountered a few interesting ones that I'm happy to relay. Wonder and Wickedness looks pretty cool. Hamsterish Hoard of Hexes does as well. I recently found this bizarrely named one here on itch (and it's free). Lastly, there's an RPG called Knave that has an optional list of 100 levelless spells.