I use a combination of all the ones listed in this thread. Ualaa has some great advice in that you don't want all of these addons on all of your toons. For example, Recount is great in analyzing how members of your team are doing in action. But I noticed drastic slowdown by running this on multiple clients and now only run it on my main.

My favorite mod in the list is SmartBuff. I ran a focus based buffing system before I was introduced to this mod. Not only does this speed things up ... it also saves bar space. Give it a try!

PS - I view Jamba as a requirement. I couldn't imagine 5 boxing without this mod.