This is a list of all the filters (plugins) I've written for MCEdit. You can download MCEdit here.
Adds an item stack to a container. If you select a 1x1x1 region of air, it will create a chest for you and add the item stack.
Select a region and apply potion effects to all mobs in that region.
Create 3D animations. Build all the frames next to each other, each with a constant width. Select all the frames at once, enter the width of the frames, and the player detection range you'd like, as well as the number of ticks (which are 50 milliseconds) for each frame.
Select a region and run the filter. The filter will change the world's seed to one where there are no slime chunks in the specified region. It doesn't always work, though, because it can't always find an appropriate seed.
Select a region and apply certain properties to all entities in the region. Good for modifying FallingSand entities.
Select a region and apply attributes to all mobs in that region. Can be used to set most properties that aren't settable during gameplay.
Put leather armor into a dispenser or chest, then select the dispenser/chest, and you can change the color of the armor.
Select command blocks and you can set their color, and various other display attributes.
Select a bunch of circuitry and ColorWires will separate the different redstone wires and colorcode them. May not work if you use top-slabs in your circuitry.
Select a bunch of spawners and run the filter, it will combine them into a single spawner which randomly picks between the spawns. Put a sign on top of a spawner to give it a custom randomization weight--the default is 1.
Place some signs. These signs should have a single word on them. For example, if a sign says "tele" on it, you can create a command block with "/tp @a[#tele,rm=10] $tele". This command block will teleport anyone farther than 10 blocks away from the "tele" sign to it. It also removes the sign when you run the filter.
Place some wool guides and CreateBusses will create the wires for you.
Put armor into a chest and run the filter on the chest to create a mob wearing that armor. The slots are, in order: Held item, boots, legs, chest, head.