Kriss' Interface. More details to come.

It doesn't get much more Vanilla than this. The only mods I use is CT_RaidAssist and Atlas.

The bottom row is the primary offensive spells. From left to right, Wand, Smite, Mind Blast, Shadow Word: Pain, Focused Casting (1 minute cooldown, prevents loss of casting time from damage), Renew (a Macro which selected the appropiate level based on the target), Inner Fire, Fade, Power Word: Shield (a macro which again selects the appropiate level based on the target level), Shackle Undead, Psychic Scream, and Mana Burn.

These are sorta offensive, defensive, But it's what I'd use on a day to day basis if I were to solo.

The next row above, from Left to Right. Flash Heal, Greater Heal Rank 2, Rank 3 and Rank 4, Prayer of Healing, Dispel, Cure Disease, Abolish Disease, Feedback, Power Word: Fortitude, Inner Focus (free spell, that also crits if possible), and Mana Potions.

The rest are really infrequently used and are layed out as needed. Lower Right Bar is keymapped, but not very well.

I use 1-9 for the bottom. Option 1-9 for the top, Shift-Option 1-9 for the bottom right. Which in practice doesn't get used except for Shift-Option-= to mount and unmount.