Sometimes being an Engineer (or one of the other tradeskills) means you're fiddling with heaps upon heaps of separate little twiddly items before being able to build up your masterwork gadgetry. Reverse Engineering will turn you around on your head. Now you can work from a top down perspective. Simply open your Tradeskill panel up to the desired object, then click on the icon for any part that requires construction, and voila, you'll be scrolled directly to that item. Not only that, but there's a handy 'pop back' button that will pop you back up the stack to your previous location!
You'll be able to instantly see what parts are craftable by the cog indicator that will appear when you mouse over the item.

v3.1.1 - Updated for WotLK and 3.1
v3 - Removed all libraries. Uneccessary overhead cause this is a simple mod...
v2.0.3 - Note to self, adding reference to toc doesn't help if you don't add the library to the libs
v2.0.2 - Fixed yet another library reference... Where are they coming from? =P Hopefully people can use it now...
v2.0.1 - Fixed a missing library reference
v2.0 - WoW 2.0 compatible. Ace2. Cleaned up a whole lotta code. Suggestions for features welcome despite the small scope of the project.
v1.6.3 - Made it so that it didn't jump when shift is pressed to allow linking of materials
v1.6.2 - Fixed a FreezeFrame error
v1.6.1 - Fixed a 'bad argument #1 to `find' (string expected, got nil)' error
v1.6 - Updated to play better with KC-Enhanced Trades and deal with a "Bad skill line in ExpandTradeSkillSubClass" error.
v1.1 - Er. *cough* due to a last minute rename of the addon before I put it up, it didn't actually load =) All fixed though now. Also, I made it so that it unfilters when you click down, so filtering will be removed when you drill