ZR
Zero Radiation

ZS

I'm just catching up on my zs. *Snore*

ZT
Zoo Tycoon!

ZU

it's kinda like a Zoo, but in a language other than english

ZV
Zoomed Videos

ZW

Zowie Wowie!

Edit: oops, wrong thread! xD;

ZX

Zebra Xenophobia

ZY

Irish vehicle registration for Louth

(Interesting what tidbits one can find on Google)

Also - lol Trys. :D

ZZ
Zero to Zion

AAA!!!

yaay! triple digits!

also, American Automobile Association.

AAB
Automatic Alternative Billing

AAC

Automatic Air Conditioning

AAD
Armed And Dangerous

AAE

Alcohol After Effects

AAF
Alien Ant Farm!

AAG

Alien Anti-Gravity