db4o is a preferred choice for educational and research institutions, for instance:

• Glasgow Caledonian University - Department of Computer Science, Glasgow, United Kingdom
  Prof. Jim Paterson: "The sheer simplicity of the way in which you store objects with db4o is also attractive for teaching purposes. [...] For students learning how to apply object-oriented concepts in their projects, the need to interface with a relational database can have a negative influence on their approach to design of their domain models. Using db4o allows them to work with persistent data without the distraction of conflicting data models and without the need to spend a significant amount of time learning to use a tool such as Hibernate or a complex OODBMS."
  
  Download Jim Paterson's lecture notes or script on object persistence.
  
  
• Texas A&M University - Biology Department, College Station, TX, USA
  Used for research and teaching purposes. Adam Stevenson, Biology Graduate: "We have found db4o's technology is an invaluable research tool. We are impressing with results coming from simulations that require db4o. I am currently modeling the molecular genetics of circadian rhythms in Neurospora Crassa, a species of fungus, and using it to study information theory. We would not be able to model object structures as complex, numerous and dynamic as ours if we had not chosen db4o as our persistence tool, because it is non-intrusive, allows us to change object models easily and its low memory requirements."
  
  Download Adam Stevenson's lecture notes (PPT | PDF) on object persistence.
  
  
• TFH Berlin - Department of Computer Science, Berlin, Germany
  Prof. Stefan Edlich: "Due to the simple though powerful API, the impressive performance and the direct persistence of complex objects, db4o is our first choice for teaching purposes as well as for developing large-scale industry portals"
  
  Download Stefan Edlich's lecture notes on db4o (in German).
  
  
• University of California - Lawrence Livermore National Labs, Livermore, CA/USA
  Researcher Dominique Toppani: "We are developing management tools for biological experimentations and a software for protein crystallization. These projects do not involve millions of records, but need complex and flexible objects. Anything with SQL writing would be a nightmare to use. I looked at object to relational database mapping. I tried it for a week but it did not save me much time and required me to derive all my objects from their model. It was not good! I then found db4o and right now, I don't see anything else I would want to use."
  
  
• Westfälische Wilhelms-Universität - Institute for Geoinformatics, Münster, Germany
  in collaboration with Energy Research Center, Temixco, Mexico
  Creation of a comprehensive web-accessible database for geochemical data. Researcher Andreas Jaeger: "We have chosen db4o because of its seamless integration with object-oriented development in Java: easy handling of hierarchical data structures, semaphore support, complete query support via evaluations. The learning curve for the database is extremely low, the support is great, both make it a good choice for scientists of all fields of study, regardless of their programming skills."
  
  

For more educational and research resources visit ODBMS.ORG, sponsored by db4objects.