Raid frames
Grid
"Grid is a modular, lightweight, and
screen-estate saving grid of
party/raid unit frames."
A very good raid frame which is very
useful for healers. (Clbull)
Note: it can take a lot of fiddling to
set up how you like it, but lots of
tutorials exist for it and once you
get the hang of it, it's easy.
(lilserf)
Click-bindings
Clique "Clique is a simple GUI that lets you assign click-casting
for any number of unit frames. Click
casting allows you to define the
behavior the game takes when you click
on a frame. This can be casting
spells, running a macro, using an
item, or something as simple as
changing targets or assisting a unit."
Excellent when used with Grid to let
you bind various clicks (right, left,
middle, shift-left, etc) to different
spells. (lilserf)
Cleansing
Decursive "Decursive is a cleansing mod intended to render
affliction removal easy, effective and
fun for all the classes having this
ability."
I use Decursive, and I believe it (or
a similar addon) is not only helpful,
but imperative. (Hhoky)
All-in-one
VuhDo "VuhDo is a raid monitor similar to CTRaidAssist or
Blizzards built-in raid frames.
Basically this is about displaying the
health of raid members in form of
clearly arranged bars. VuhDo is
primarily directed to healing classes,
but will make use to almost any other
class. Moreover several healing spells
or other actions can be asserted to
mouse clicks on those bars
(Click-Heal)."
This is a solid replacement for Grid,
Clique, Healbot, what-have-you. Full
raid frames, ability to bind spells
(and Macros!) to key and mouse clicks
on those frames, integration with the
incoming heals libraries so you can
tell when someone is going to be fine
or not, ability to display HoTs
easily, and best of all -- it works
out of the box. Grid can take some
time to set up properly, but VuhDo
just works. (Celairia)
Player versus Player
Gladius "Gladius adds enemy unit frames to arenas for easier
targeting and focusing. It is highly
configurable and you can disable most
features of this addon."
Gladius is every arena player's dream.
Just like VuhDo it will run out of the
box; you can simply drag the window to
where you'd like and enter an arena.
However, if customisation is your
forté then there will be plenty to
keep you busy. In addition to the
usual Blizzard UI features of tracking
health/mana counts and spellcasting,
(albeit in a prettier way,) Gladius
tracks enemy trinket up/downtime and
drinking/first-aiding, as well as
several important buffs and cooldowns.
(Roble)
Miscellanenous
VisualHeal "VisualHeal is a small and simple but powerful tool
for all classes that visually shows
your heals to others and heals
incoming to you from others by means
of two information-packed, yet
intuitive bars."
It shows all incoming heals to my
target (great for watching overheals,
or interrupting heals to maximize raid
healing). (Hhoky)
SmartRes "SmartRes puts bars on your screen that have timers
for the various resurection spells:
Resurrection, Ancestral Spirit,
Revive, Redemption, and tells you who
is casting on whom, how long it will
take to bring the target back to
life."
I also use an incoming Rez addon,
called SmartRes, but that's just my
personal preference, to maximize
rez's. (Hhoky)
Class-specific
PoMTracker "A mod that tracks who Prayer of Mending is
jumping to and how many charges you
have left. Displaying it in a small
movable window frame." (Hhoky)
Best Answer
Yes there is.
You can actually do that by adding another add-on on top what you have already ! His name is pretty explicit : Addon usage
If the lag you are talking about is in fact fps drops, look at the CPU usage of each add-on you use to determine which one is using the most, repeat this process until your fps stay constant and you should be good, or you can sacrifice a lot of small add-ons to keep the core ones, that's up to you.
Read carefully the page to have full details and subtilities of the add-on.