Spirit Guide is An Unconventional mana Regeneration Calculator that cleans up previously shady aspects of the relationship between mana regeneration and many complex factors such as item procs and talents.
Anyone who does not know what the 5 second rule is, i suggest you look away now.

for those of you who do not know what it is, but defied me by continuing to read, a good explantion of the 5 second rule (5SR) can be found on wowwiki:
 http://www.wowwiki.com/Mana_regeneration
                                                                        
This is My first Addon,
It is designed to calculate different combat scenarios for healers or any class intrested in their mana regen.
Since 2.4 there has been a great uncertainty on how best to get more out of your character should i get more intellect or spirit ? well originally someone said get twice as much spirit as intellect, and thats stuck, but the relationship is alot more complex.

What does Spirit Guide do and why dosent it give me my actual mana regen when i put in all my stats?
Spirit Guide calculates predicted mana regen over the course of a fight and uses it to give advice on the value of spirit compared to intellect, this is different to your "mana regen" in your character sheet for a number of reasons: first of all your mana regen shown in your charcter tab is an idillic situation where you gain 100% of your spirit based mana regeneration all of the time, whereas in combat this isnt the case. Spirit guide calculates beneft from items and talents. Spirit Guide uses your mana pool as "bonous mana" and spreads it out over the course of the fight, in this way it allows you to calculate the value of intellect as affected by fight duration.
Thus theoretically it is possible to calculate your actual mana regen by removing all talents, setting % time in 5sr to 0 and removing the include base mana option.

Known Bugs:
 -On startup the minimap button causes two errors, these do not affect the functionality of Spirit Guide, but are just annoying. Some People may not notice this error, it depends upon what error catcher (if any) you are using.

Calculates:
 -Mana Regeneration
 -Mana Regenerated over fight length
 -The Worth of Intellect as "Bonous Mana" over the period of a fight
 -Mana Gain from spells such as Innervate Evocation and mana Tide Totem
 -The Mana Regeneration Coefficient
 -The Percent of time Procs like Bangle of Endless Blessings and Darkmoon Card Blue Dragon are active
 -Advice on weapon types to use during innervate

Draws Graphs of Mana Regeneration afffected by:
 -Intellect
 -Spirit
 -(more soon)

Takes into account:
 -Spirit
 -Intellect
 -Mp5 from Items
 -Class
 -Fight Length
 -Cast Frequency
 -% Time in 5SR
 -Innervate Count
 -Evocation Count
 -Mana Tide Totem Count
 -Bonous Stats on Innervate weapons

Player talents / Spells:
 -Intensity
 -Meditation
 -Arcane meditation
 -Dreamstate
 -Mage Armor

Items:
 -Bangle Of Endless Blessings
 -Darkmoon Card: Blue Dragon
 -Primal Mooncloth Set Bonous

Coming soon:
 -More Graphs (together with labelled axis)

A note on Expansion:
 This Mod has huge scope for expansion, but for those of you who want to keep it pure and simple i will also try to keep the confusion minimal by hiding all those extra options where you cant see them :)
 Some ideas i have already thought of are:
 Average mana use per cast which would make the innervate weapon advice hugely more accurate as currently it does not take into account they you are using mana while innervate is active.
 A battle recorder that records your cast frequency, time in 5sr, lots and lots of new variables, and be able to tell you how long untill you go out of mana. since i only started programming 3 weeks ago, i'd have to do much more work before i got to this standard.
 Feel free to post new ideas and suggestions in the commments.

Credits:
 Phae - For some wonderful theorycrafting
 Andridge - For a beautifully created icon.
 Gararf - me for learning how to make an addon from scratch.

The web based version of this calculator can be found at:
http://www.resto4life.com/guides/calculator-mana-regeneration/
 along with the detailed theorycrafting on how this calculator works.