Java serving 1 billion pages per day for eBay! I'm always looking for Java case studies. It's fascinating to see just what people have done. This set from JavaOne lists eBay, The Wall Street Journal, American Airlines, several huge governmental organizations, and many more.
I love looking through case studies. They can teach you so much about what to do, what not to do, what is in vogue, etc. All those useful design patterns came from analyzing lots of case studies and seeing what worked; and sometimes, more importantly, what didn't work.
So this year I decided to start listing case studies when I find them. And a great place to start is JavaOne, where lots of the really big case studies get presented. So here they are. The highlights for me: eBay architected for 1 billion page views a day; The Brazilian National Health handling 100 million outpatient procedues a month; 24 million Java Cards used by Taiwan Health Insurance; Capital One Financial handling 80 million transactions each month.
Speech synthesis comparison of existing C product (Flite) and Java implementation (FreeTTS): Before performance tuning Java takes twice as long as C; after performance tuning Java takes one third as long as C and has better horizontal scalability.