The following types of searches can be done with the geocaching.com search block on the WGA website:

Keyword
XXXXXXX
(word or words to search for)
Example: zebra (view example results)

Waypoint Code
GCXXXX
Example: GCHZKB (view example results)

Zip Code
#####
(normally does not show caches you hid or already found... append a + to see these caches)
Example: 53001 (view example results)
Example: 53001+ (view example results)

Area Code
###
Example: 608 (view example results)

Show State Summary Page
XX
(two letter state abbreviation)
Example: WY (view example results)

Show New Caches By State
new: XX
(two letter state abbreviation or geocaching.com state ID number)
(if no state is provided, WI is assumed)
Example: new (view example results)
Example: new: SD (view example results)
Example: new: 50 (view example results)

By Location Name
loc: XXXXXX
(name of city or town in Wisconsin)
(normally does not show caches you hid or already found... append a + to see these caches)
Example: loc: Wisconsin Dells (view example results)
Example: loc: Belgium+ (view example results)

Track Travel Bugs/Geocoins By Tracking Number
TBXXXX
(public travel bug reference number with TB prefix)
(or 6 character private travel bug tracking number with 'TB' added in front of it)
Example: TBV620 (view example results)
Example: TBC618XP (view example results)

Geocaching.com Profile For User
profile: username
Example: profile: Jeremy (view example results)

Geocaches Found By User
found: username
Example: found: Jeremy (view example results)

Geocaches Hidden By User
hidden: username
Example: hidden: Jeremy (view example results)

If a blank search string is provided (i.e. you don't enter anything into the search box), you are directed to the Wisconsin state summary page on geocaching.com.