I first posted this here but this is an expanded version:

AAdvantage routes to European hubs
where "hub" is an airport with flights on an AA partner other than to its hub

AA via
LA (LHR)
Dallas (LGW, ZRH)
Chicago (LHR,BRU,DUB,MAN)
New York (LHR,BRU,DUB,MAN [AA codeshare],ZRH)
Boston (LHR,MAN)
Miami (LHR, MAD, MAN)
Raleigh (LGW)

British Airways to LHR via
Mexico City
Vancouver
Toronto
Montreal
to LGW via
Antigua
Barbados
Kingston, Jamaica
Bermuda

Finnair to HEL via
New York

Iberia to MAD via
New York
Miami
Chicago
San Juan

Aer Lingus to DUB via
Los Angeles
Boston
New York
Chicago

Swiss (for now) to ZRH via
Los Angeles
Chicago
Miami
Boston
New York
Montreal

Turkish to IST via
Chicago
New York

There are also AA flights to Paris (ORD, JFK, BOS, MIA, DFW), Rome (ORD, JFK), Glasgow (ORD), and Frankfurt (ORD, DFW), and AA and EI flights to Shannon (ORD, BOS, JFK) and probably some others. Other than the usual suspects, remember that Air Tahiti Nui has a flight from LA to Paris.

For OneWorld awards, just ignore the non-OW airlines in the list...

Good luck and have fun,

Michael

p.s. corrections and additions are most welcome