MineTweaker by Stan Hebben
Modpack and server tool enabling the addition and removal of recipes
Mob Properties by FatherToast
This mod allows you to customize all mobs, vanilla or otherwise, with completely configurable drops, attributes, equipment, potion effects, and even NBT data.
StartingInventory by DaftPVF, bspkrs
Allows you to define a list of items that will be given to the player when starting new worlds.
smp tweak util opensource
Treecapitator by DaftPVF, bspkrs, Lunatrius
Treecapitator is a mod that scares trees. Seriously, they are terrified of it.
tweak util opensource
WorldAndGenerationTweaks by Thebombzen
WorldAndGenerationTweaks provides various assorted tweaks to terrain generation.