Forgive me if a mod already provides this functionality but I haven't been able to find anything of this sort searching through WAU and the various addon sites. What I'd like to see is a mod which provides an easier to use interface in which to access the spellbook. I know a lot of people tend to set their bars then just move on, perhaps never looking at their spellbooks again. I'm unfortunately somewhat of an alt-a-holic and tend to switch bar mods quite a bit to try them all out. After a while, the default spellbook interface gets quite cumbersome to navigate, having to page through multiple pages in order to find the one spell you're looking for. I recently went back to a lvl 62 druid alt of mine after not playing it for many months and had to re-set her action bars. Thumbing through all those pages, then having to remember which abilities were cat or bear and whatnot really felt cumbersome using the default UI. Just an idea I hope someone finds interesting and would be willing to give it a shot.
While i got nothing against such a Addon, i think its basically a waste of time to write. Imho Blizzard could easily change the whole Spellbook into a much more useable form... by just removing the cluttering as every damn rank has their own Place in the spellbook...there is no reason for that tbh....but well its Blizzard :)
Never seen a Game with a Spellbook like that (i didnt play all games so there might be some)
I was toying with this idea earlier, came up with this:
 Conjure Water
 Arcane Explosion
And, as a bonus, the first default page would be a shortcut page, maybe a 7*10 grid of action buttons, so that you can keep your OOC spells in there, and yet organized to your tastes. Big examples of what would go on this page would be professions, conjures, teleports, portals, possibly emotes (especially of the advert kind).