10gen, the company behind MongoDB, will be offering some free webinars this fall. This webinar series is targeted at using MongoDB with Java. 10gen has been running successful webinars for a long time, so I would high recommend any/all of the following sessions.

Title Date
Building your first Java Application with MongoDB Oct. 18, 2012 and Nov. 22, 2012
Building Web Applications with MongoDB and Spring Nov. 1, 2012
MongoDB on the JVM Nov. 29, 2012
Simplifying Persistence for Java and MongoDB Dec. 13, 2012