FOAF repository

I don't know of any repositories but if you Google filetype:foaf it will return .foaf files in it's index. You can be more specific so

smith filetype:foaf

Will return .foaf files with the word smith in them. I haven't played too much with this, but I'd imagine it could help.

I would have pointed you to pingthesemanticweb.com but that service seems to be offline.

You could also look through the contents of the BTC-2012 dataset. This will contain a lot of FOAF data alongside other stuff. You could filter the data you need from the dumps.

You could also try queries against the LOD cache SPARQL endpoint. Here's one idea:

SELECT DISTINCT ?g
WHERE { GRAPH ?g { ?d a foaf:PersonalProfileDocument } }

And here's some LIMIT 100 results for that query.

You could also try something similar over at Sindice.

I should add that a lot of FOAF data available on the Web comes from a small number of sites like livejournal.com, identi.ca, vox.com, etc. They export a FOAF profile for each of their users, culminating in millions upon millions of FOAF files on the Web. It's important to be aware of this as these exporters greatly outnumber the "homegrown" FOAF files on the Web, and due to the uniformity of their export code, they can often "skew" distributions and other analysis of large-scale RDF data crawled from the Web. For example, you'll find a lot of FOAF files contain a "social outdegree" of precisely 1,000 simply because such sites limit the number of connections you can have.