For the ones I listed below you can find out the contact info by going on FREIDA or Google. This list is by no means complete. Please feel free to add to it.
Externships
1) Cedars-Sinai Medical Center
This is where I did mine. This in Los Angeles and is flexible and allows for a variety of experiences including research. It is a beautiful hospital located a block from Beverly Hills.
2) Long Island Jewish
I heard this is a good program and it does sound like a good experience. It is in New York.
3) St. Elizabeth's
This is in Washington D.C. It seems rigid and the program does not seem as nice as the above 2.
4) Jamaica or Brookdale (cant remember which one.)
This is in New York City. It is rigid and it is IMG friendly. They tend to prematch a lot of the externs.
5) NYMC (New York Medical College)
This is in Vallhalla in Westchester county just north of New York City. Seems better than #4 and #5. I think it is an externship.
6) Houston, Texas Veterans Affars hospital (the largest federal building after the Pentagon)
This one entails a lot of paper work. Also you could try Baylor and UT Houston.
Observerships
I believe the ones listed below are all observerhips. I dont think they are externships.
1) University of Mississippi Medical Center Program in Jackson Mississippi
2) one of the Alabama programs (not the one in Mobile)
3) i beleive one of the New Jersey programs
4) Mt. Sinai Med Center in Miami Beach
They dont have psych but they do have memory disorders. I did this one as well and enjoyed it. They call it a mini-residency.
5) Buffalo, New York
Research
I don't have much information on this. I had an offer in White Plains, NY. Heard of someone doing one in UIC or somewhere in Chicago. You can also try and do some research duing your externship. I believe the best way to find one is to email every psychiatry program and look around in the forums.