The default interface does display them, you know.
Other than that, X-Perl has a neat CP display, and even shows druid mana while in feral forms (though not energy while in caster)
For yet another way of tracking CPs, I suggest InlineAura, which displays them as a number on the actual action buttons of CP consuming abilities.

The OP was responding to the question in the queue about addons dropping frame rate, not which ones to use.

My bad, misread that comment :B

I'm a big fan of Rogue Focus Classic. It's been abandoned, but someone updated it to 1.3.1, the link to download is http://wow.curseforge.com/addons/rogue-focus-classic/repositories/dridzt_rfc_cata/files/

Small movable box of bars on your screen that shows your health, number of combo points, your energy regen, and your target's health. In spite of being outdated, it works very well.

I actually had a very similar issue with my Shaman a couple weeks ago, during Love is in the Air when I was farming an instance for love charms. I did exactly as the Queue suggests today by disabling my add-ons and gradual enabling them to see which one was causing the issue.

To my great surprise, Deadly Boss Mods was the add-on that was causing the massive frame-rate drop whenever I'd pull a couple mobs. It was very weird since I'd been farming charms in the same place just the night before with no issues, and there were no patches that I knew of. (Although, it's possible that a hotfix patch downloaded in the background while I played that I just didn't notice...) I ended up going into my add-on folder and completely deleting DBM, then reinstalling it. I didn't have any issues after that. It was odd.

Check out the addon Hear Kitty. Rather than fill my screen with graphics, I love this addon because it provides you combo point (and holy power!) information audibly by playing tones. After a while, it becomes second-nature to know your level just by listening... and it feels like its always been part of the game :)

A while ago i had a similar issue, it just turned out that i hadn't reset recount for a while on 1 toon, so it was storing a lot of data.