BeyondPotions

Procedurally generates potion recipes for every item in the game! To craft, simply add your ingredient at the top of the brewing stand, and it will start and finish just like a vanilla recipe.

Most recipes will produce junk. And when they don't produce junk, it usually comes at some cost.
Note that using the same ingredient will usually produce the same recipe twice, and you'll usually need to start with awkward potions, but there are a few special circumstances. It's like a puzzle, except I don't tell you where the pieces are, and every server has it slightly different...
All custom potion recipes are based on a seed: you can change the seed whenever to reset all brewing recipes, and they should stay the same across minecraft versions (except a few recipes using new potion effects.) You can even share and borrow seeds if they produce interesting results.

Somewhat configurable. By default, potions never generate with uselessly high levels; never use values that render incorrectly (7+); and a few potions are limited for balance reasons. But you can always make it stricter, or ignore these limits altogether.
There are also a few cheats you can enable if you want to test out the plugin before deploying to your server, to speed up brewing and remove the costs.

Compatible with redstone, glowstone, gunpowder and dragon's breath.

If I use an ingredient on top of an existing potion, do the effects stack?
Say less.

The length of both effects is cut in half. And you can do this as many times as you'd like. That seems to be enough to balance things out - as absurd as that potion looks, it's pretty much useless.

I want to add my own recipes!
There are other plugins that accomplish this; take a look at WolfyScript's custom crafting. If you're a plugin designer, you can also take at this (somewhat incomplete) tutorial that I used as a starting point. As for this plugin: it's not really the point!

Many of the bugs with the previous version have been fixed. Thank you for your support!