Quote – Get stock information
HZQUOTE+symb.symb@hz.com
Stock – Get detailed stock information
HZSTOCK+symb.symb@hz.com
HZJOKE@hz.com – Get a joke
Weather – Get weather
HZWEATHER+zip@hz.com
TAFMETAR – Get TAF and METAR info
HZTAFMETAR+ident@hz.com
Nextflight – Next flight between airports
HZNEXTFLIGHT+airport.airport@hz.com
FlightInfo – Get current flight status info
HZFLIGHTINFO+airline.flightnum@hz.com
Address – Lookup address from phone number
HZADDRESS@hz.com – Phone number in subject
Define – Get a definition
HZDEFINE@hz.com – word in subject
Birthday – Get famous birthdays for today
HZBIRTHDAYS@hz.com
Areacode – Get info about areacode
HZAREACODE@hz.com – Put areacode in subject
KnockKnock – Get a knock knock joke.
HZKNOCKKNOCK@hz.com
Gasprices – Get gas prices for zipcode
HZGASPRICES+zipcode@hz.com
Lottery – Get lottery information
HZLOTTERY+state@hz.com
Exchangerates – Get current exchange rates
HZEXCHANGERATES@hz.com
Walmart – Get Walmart locations near zipcode
HZWALMART@hz.com – put zipcode in subject
Airport – Get airport technical information
HZAIRPORT+ident@hz.com
Tailnumber – Get aircraft information
HZTAILNUMBER@hz.com – put tailnumber in subject
Aviation Weather – Get aviation weather informaton
HZAVIATIONWEATHER+ident@hz.com
Starbucks – Get Starbucks locations near zipcode
HZSTARBUCKS@hz.com – put zipcode in subject
Letterman – Who is on Letterman and his TopTen list
HZLETTERMAN@hz.com
Directions – Get driving directions
HZDIRECTIONS@hz.com – put start and end in subject
Movies – Get local movie theatre information
HZMOVIES+zipcode@hz.com
EBay – Get Ebay auction information
HZEBAY+auctionnumber@hz.com
Earthquakes – Get earthquake information
HZEARTHQUAKES+world@hz.com – world wide earthquakes
Whois – Get Whois info
HZWHOIS@hz.com – domain in subject
Local – Get Google Local results
HZLOCAL+keyword+zip@hz.com
News – Get Google News stories
HZNEWS+Category@hz.com
Horoscope – Get todays horoscope
HZHOROSCOPE+sign@hz.com

[NOTE: I remember there used to be a service just like this a few years ago before the dot-com crash, but I can't remember what it was called. Consider these permanent parts of my address book. I'd love 'em to do something with Gada.be, too.]