The folks over at Pingdom in their Royal Pingdom Blog have collected the financial information of some of the most popular open source software companies.
No surprise that it is only Red Hat so far that has had runaway success with a business model purely around open source. They are a publicly listed company, and in a partner event I attended last year, made a big deal about the fact that their revenues have been consistenly growing year on year and are well over US $500 million (and if their growth continues, will join the mythical billion dollar club of Microsoft, SAP, Oracle soon if they are not acquired or bought out first along the way).
For Novell and Sun Microsystems, the money they make from open source software is harder to pin down as they are large, very diversified companies (but with open source a key component of their strategy--as the recent acquisition of MySQL by Sun and SuSE by Novell has shown). Same goes for IBM or Oracle.