As requested, information from my 'Raid Addons' post that i feel are specifically useful for mages:
Power Auras
A love this mod on my mage as it gives me visual and/or audio prompts when situation procs become available i.e. clear casting/ arcane barrage / hot streak. It means you no longer have to have half an eye on the buff bar watching out for these procs. Would also work on trinket procs etc. and can be configured to show timers.
It can also be set up to monitor the number of stacks on a target i.e. arcane blast, scorch stacks etc.
http://wow.curse.com/downloads/wow-addo ... assic.aspx
Casting Bars (Quartz)
Another mod which has evolved with time but i still use it for its original conception. The reason this one caught my eye was the claim that it can increase a spell casting dps' damage by 10-20%!
In its basic form it is simply a replacement for the standard Blizzard casting bar but alot 'smarter'. It takes into account things such as mob distance, latency and other factors to give a more accurate reading of cast times. This allows quicker casting of the next spell thus squeezing out as much dps as possible. It has many different modules associated with the mod and i myself am only just getting to grips with it.
I feel that it is one of those mods that once you try, you couldnt even consider going back to the standard UI version.
http://wow.curse.com/downloads/wow-addo ... uartz.aspx