NEI is very useful.
I do actually agree with TheArmyGuy.
Players shouldn't have to rely on wikis nor mods to be able to craft the more complex stuff.
Though i am pretty sure that finding out crafting recipes is part of the magic of Minecraft.
On the other hand, some of the more complex items (redstone comperator and the such) are hard to understand for some people, let alone finding out how to craft them.
Some findable books or something might help, i am not sure though.
At least something to explain and show the newer players that there is some more complex stuff you can do.