I would like to see how is Builder pattern used in real world applications/APIs. The examples I found are all pizzas, cakes, cars et cetera (plus the parser example from the GoF
Update: I recently came across an even better example (imo). Checkout the JobBuilder and TriggerBuilder implementations in the Quartz scheduler package: http://quartz-scheduler.org/api/2.1.5/
Also, when I have time, just for fun/practice, I try to write examples of all GoF patterns in java. Just recently, I used the Builder pattern to make it easy to generate different types of Sitemaps (google site map vs, html site map, etc). The code is in java, but you might be useful: https://github.com/dparoulek/java-koans/tree/master/src/main/java/com/upgradingdave/koans/builder
Good question, I'd be interested in seeing more modern examples too.