Yabber allows you to customize the chat bubbles that appear above characters' heads when they speak. Are they too big for you? Make them smaller. Don't like the color of the text? Change it. Don't want bubbles at all? Change the display to just single text items above heads, or turn floating chat off completely. It's up to you.

To access Yabber in-game, type /yab or /yabber.

Note: This addon REQUIRES you to have LibSlash installed! You can download LibSlash from the WAR section of Curse: http://war.curse.com/downloads/details/13510/