Every buff, debuff, cooldown-ability and proc in World of Warcraft has a spell ID. Many trigger effects that you don't normally see in-game also have spell IDs. Spell IDs are language-insensitive and unique.
This is really only relevant to a few people... for example, if you manually configure you timer bar addon and wish to do so by using spell IDs rather than spell names (I prefer spell IDs because I sometimes change my client's language).
Hope you like it,
EDIT: it's not 100% complete. many pet buffs & debuffs are missing, but those usually have one single entry in wowhead, so there's no ambiguity. the above link allows editing, if you'd like to contribute.