Recommended Mods

[FlyingMongoose]

So, I figure enough of you make use of mods, why don't we have a recommendation thread. Here's what I have so far.

Start with sk89q's launcher
http://build.sk89q.com/job/SKMCLauncher/

Get ModLoader (it's a prerequisite for a ton of mods anyway)
Minecraft Forum Link to Thread

Rei's Minimap is a powerful and very useful tool.
Minecraft Forum Link to Thread

Inventory Tweaks is great for keeping things organized
Minecraft Forum Link to Thread

If you use WorldEdit you NEED the CUI
sk89q's Wiki info page

MAtmos is a beautiful sound mod (the mod loader can not load this, but instructions are in the zip file)
Minecraft Forum Link to Thread