I found a nice illustrated guide to 9 of the most common Espresso based drinks on the interenet. I spoke to the author of them and he has released them under a Creative commons license so we can use them on the Underground site, Thanks Lokesh :-)

Espresso [ess-press-oh]	Espresso Macchiato [ess-press-oh mock-e-ah-toe]	Espresso con Panna [ess-press-oh kon pawn-nah]
Caffé Latte [caf-ay lah-tey]	Flat White	Cafe Breve [caf-ay brev-ay]
Cappuccino [kapp-oo-chee-noh]	Caffé Mocha [caf-ay moh-kuh]	Americano [uh-mer-i-kan-oh]