E.g. Wikia. Get lots of users, show them ads.
Like BountySource or (some other newer site whose name I forgot that claims to do it better). But see the problem.
E.g. Ghostscript, dual-licensed GPL and commercial. Or artists (are there examples?) who CC non-commercial their work, and also sell it separately.
E.g. those PayPal buttons you see on some webpages "Donate Now", or Bitcoin addresses.
E.g. Red Hat, and companies that support free stuff though it's not directly their business, like IBM, Google, ...?
E.g. vWorker, Jan's business.
E.g. those things Wikipedia runs periodically
E.g. Flattr, TipTheWeb.
Sell auxiliary services around a free product.
What is free culture
- free software: GNU, Linux, *BSD, ReactOS, KDE, LibreOffice, so many others
- free articles: Wikipedia, other wikis, nicely licensed blogs
- free artwork/music: Mutopia, IMSLP, lots of Flickr, (probably lots of famous Creative Commons art sites I don't use),