Just thought I'd throw up a list of ones that I consider "must haves" for me..
Titan Panel : this mod is very adaptable.. it has plugins for just about everything ya could want.. its an all around good one.

Necrosis LDC : this is a Warlock only mod, it has all of our pet spells, summoning spells, and stone spells as well as it's own DoT timer in a groovy, yet intuitive format with several built in features (fear imunity warning/shadow trance alert) great for any Warlock.

ItemRack : is just damn handy.. that's it, you can easily switch out gear, depending on the fight (or wipe), also it comes in it's own flavor or as an add-on for Titan Panel.

DoTimer : is an alternative timer that I have had a great deal of success with as far as keeping track of banishes and DoT's, It is updated regularly & I am now recomending it, as my timer of choice.

SpellTips : is an addon that will modify your tooltips to show approximately how much damage or healing a spell will really do with +dmg/healing gear equiped. You can still see the base damage/healing of the spell by looking at it in the spellbook. It is simplistic by design and coded to be very efficient.