While Minecraft Forge is not required if it isn't installed you won't be able to see mobs in mobspawner items.

The process for installing NEI has changed. (For the easier AGAIN!).

Install FML 3.0.175.332+ OR MinecraftForge 4.0.0.240+ into the jar.
Place the CodeChickenCore jar file into the coremods folder.
Place the NEI jar file into the coremods folder.
Place any modules' zip files in the mods folder.

NotEnoughItems. Provides: All NEI functionality.
Download
Source
Bukkit Port by cpw.
Bukkit

RedPower Config Module. Provides: RedPower Subset Tags, Alloy Furnace recipies and Showing of all MicroBlocks. Requires: NotEnoughItems+RedPower.
RP_Plugin

Mistaqur has plugins for Thaumcraft, Buildcraft, Forestry, Railcraft and an IC2 fix at https://bitbucket.or...ugins/wiki/Home