I dunno but the blessing of talos (praying at a talos altar) is supposed to reduce them. It seems to be totally glitched though and doesn't do anything. Or at least it doesn't for me. It says it reduces time between shouts by 0%.
"I'm not reading reviews when I can just ask this board." - TormakSaber asking about a Sam & Max game on the TF2 board
Amulet of Talos reduces shout cooldown by 20%, and the blessing from the shrine of talos (behind the noisy guy in whiterun, at the base of the steps to dragonsreach) also reduces cooldown by 20%. They do stack to 40%.
there's also the console:
player.setav shoutrecoverymult 0
that reduces shout cooldown to zero
player.setav shoutrecoverymult 0.5 reduces it by half