I've taken a challenge to provide power to a server of 6 using only what can be provided with a single 10x15 cursed earth mob farm. I've added a pair of witch spawners and a blaze spawner inside, and let me tell you, you have a ton of options.
Mob Essence + Gunpowder -> Reactant Dynamos
Redstone -> Magma Crucible -> Heated Redstone Generator
Potions -> Potion Generator
Sugar -> Redstone Furnace -> Survivalist Generator
Blaze Rods -> Boilers -> BR Turbine
Enchanted Drops -> Enervation Dynamo
Ender Pearls -> Ender Generator
I'm sure there are more, but seriously, that's already a ton of power. If you see other ways to turn drops into RF, let me know. I know there is a way to do glowstone, but I don't remember it off the top of my head.