Today's post will be a short one. Work has been really crazy.
Not Enough Items (NEI) is a mod that will help you keep track of crafting recipes. In 'vanilla' Minecraft, it's purpose might not be nearly that apparent (unless you can't remember how to make an enchanting table or a beacon). It even will show various brewing recipes for that tricky brewing stand. In mods, being able to look up how to make a thingamajiger steam component thingy will save you hours and hours of time of pouring through forum posts trying to look up the crafting recipes. NEI gives you a search feature accessible from your inventory. By typing in the name (or partial name) of an item, it will pull up a catalog of all the items with that name (or descriptive text) on the right. From there, you can click on the item to see a recipe for it. The search also supports things like REGEX (a language that lets you use more fuzzy pattern matching) and can let you search for items by mod (useful for answering the question of 'What items does Thaumcraft 4 add?')
It doesn't stop there though. By right clicking on an item, NEI will pull up every recipe that uses that item. This is extremely useful for mods that add in all sorts of strange ores or items. If a mod has added a special form of crafting (and the mod author has implemented it a certain way), NEI can even show information on how to use that. Also, a little question mark on the crafting recipes will superimpose a picture of it on the crafting grid so you don't even have to remember what the recipe looks like! (There's also other features around how the recipes are displayed).
It also features a creative mode where it can give you items as if you were in creative mode. This is useful if a survival world has glitched and you lost your 64 diamond blocks. There is an enchantment selector to enchant items. Also NEI provides various buttons while in 'cheat' mode to toggle the weather, change the time, and activate a magnet mode that pulls in all nearby items. It even has a special mode that will show you were hostile monsters are able to spawn in your world (represented by yellow and red X's).
Overall, NEI is a really useful mod that really shines when extra mods are added to your game. Even in 'vanilla' Minecraft, it can help out by showing where mobs can spawn or showing what you can craft with that lapis lazuli you just mined.