FOAF-fetch is a small perl script which uses XML::FOAF to fetch address book information based on your current FOAF file. It explores your foaf:knows relationships, reading rdfs:seeAlso links to find links to other people, and then finding their contact information.
The script is very basic, and does not do a lot. It outputs the information in abook address book format, which many address books may be able to input. I haven't actually tested that. However, no matter what program you use, the data is easily human readable, and should be able to be parsed by a fairly simple script.