According to http://www.macosxhints.com/article.php?story=20070527063904285 the file Contents/Resources/English.lproj/ABAutoCompleteMappings.plist within the Safari.app package leads this list:
first
first name
fname
firstname
given name
middle initial
middleinitial
middle name
middlename
middle
last
last name
lname
lastname
surname
name
birthday
date of birth
born
job title
jobtitle
email
e-mail
street
street address
streetaddress
address1
address 1
address
city
state
zip
zipcode
zip code
postalcode
postal code
country
homephone
home phone
eveningphone
evening phone
home area code
home areacode
homeareacode
evening area code
evening areacode
eveningareacode
workphone
work phone
dayphone
day phone
daytime phone
companyphone
company phone
businessphone
business phone
work area code
work areacode
workareacode
day area code
day areacode
dayareacode
company area code
company areacode
companyareacode
business area code
business areacode
businessareacode
mobilephone
mobile phone
cellphone
cell phone
mobile area code
mobile areacode
mobileareacode
cell area code
cell areacode
cellareacode
pagerphone
pager phone
pager area code
pager areacode
pagerareacode
area code
areacode
phone
fax
organization
company