Nearby: FOAF home page | who are these people? | test run output
This is one to throw away: a quick Perl script which traverses a Web of FOAF RDF documents, using Perl regular expressions rather than a proper RDF (or even XML+namespaces) parser. It starts at a specified URL, and will continue until it runs out of documents linked by 'rdfs:seeAlso' references. See the script source for more details and a list of bugs/flaws etc.
Stop Press: I made a Ruby version too (ayf.rb). Unlike the Perl version, it uses a proper RDF parser, and so trades off reliability against installation hassles. To use, you'll need the RubyRDF library, which now experimentally includes the Liber RDF parser. That in turn requires the Ruby XMLParser package, which uses the Expat XML parser. Fortunately, these are easy to install on Unix machines, and come bundled with the Ruby Installer for Windows ( tested with ruby-167-7.exe). A test run of the ruby version's output is captured here as ruby-run1.html, and a screenshot of the images it found are also available.
Why do this? It's a zero-hassle install, with no dependencies on XML and RDF libraries of any kind. It is very rough, doesn't traverse the full FOAF Web, and doesn't make much use of the RDF documents it discovers. However, it does show the core simplicity of Semantic Web hypertext, and should give you an idea of where you could plug in more robust infrastructure (RDF parser, database, PGP signature checking), and of the kind of applications you could build with such an approach (RSS discovery, Web service discovery, distributed address books, etc...). Have a look, have fun, have a look for something better (eg. see usefulinc's foafbot pages).
The script current outputs an HTML document (which it updates continually while harvesting). The output is a proof of concept, in this case proving the concept that you can use FOAF to find pictures of people.
The Perl script itself and sample output are available.
If your FOAF / mugshot doesn't show up, the fault is almost certainly with the ayf.pl script, and not your data. See the copious disclaimers here and in the Perl code for details.