For a while now at Optaros, we've been publishing various technical white papers and reports on open source software. These aren't marketing case studies, but based on the real experience and evaluations our practise leads have put together in their respective domains. You can find the complete white paper and report list here and an RSS feed here for all the open source educational content we're developing. This work is all published under Creative Commons licenses to make it easier to use and disseminate.
A short while ago, we were guests at a UNISYS webinar on open source adoption in the content management and SOA spaces. Next week on Tues., 28 March, our own Dave Gynn will kick off the start of our own webinar series with "Open Source Adoption Trends: Where should your Enterprise Begin". Please come out and join us and let us know what you think.