A short while ago on this Blog (see the 31 January post) I talked a bit about genealogy assistance we can get from the US Immigration Service.
The Philly.com website has an article dealing with this same topic. However, rather than telling the specifics of how to get the service, it recounts a woman's experiences in using the service to get information on her grandfather. This first-hand account makes good reading, and it gives a sense of what can be accomplished using the service.
You can find the story at: http://tinyurl.com/yctrffe