I did a quick web search. Take your pick:
From http://www.grove-ent.com/nasa.html: 10-31 Suspicious person/circumstances
From http://www.911dispatch.com/information/tencode.html : 10-31 crime in progress
From http://www.10-david.com/features/tencodes.asp : 10-31 Pick Up
From http://www.provide.net/~bfield/10codes.html : 10-31 Pick Up
From http://911audio.com/radio_codes/new_york_police_fire_radio_codes_p2.htm :
ROCHESTER POLICE DEPARTMENT CODES AND SIGNALS: 10-31 Robbery In Progress
SUFFOLK COUNTY POLICE RADIO 10-CODES: 10-31 Lost Child
SYRACUSE POLICE DEPARTMENT CODES: 10-31 Subject Has Prior Record
YONKERS FIRE DEPARTMENT TEN CODES: 10-31 High-rise Building Fire
For whole country by state (and then by jurisdiction within state): http://911audio.com/radio_codes/
Note: a few places claim to have "official" or "common" lists, however from the few specific locations I checked, it doesn't look like there are standards, since they seem to vary all over the place.
To run your own web search: http://www.altavista.com/sites/search/web?q=%28%22ten+codes%22+%7C+%2210+codes%22%29+%26+%2210-31%22&kl=XX&r=&d2=0&d0=&d1=&nbq=50&pg=aq&search=Search
There are corners of the web that have gone straight to hell lately...