An alternative is Learning Aid:
http://www.wowinterface.com/download...arningAid.html
Instead of highlighting spells in your spellbook, Learning Aid opens it's own little window with the spells it determines are missing from your action bars (you can then drag the spells from the window straight to your action bars). The window also appears when you learn new spells/abilities, so you don't have to go digging through your spell book to find them!