Curt Monash published a brief overview of the OODBMS world that includes the majority of the object databases. According to him, Intersystems Caché is the most successful object-oriented database:
Intersystems Caché, the most successful OODBMS product by far, with good OLTP (OnLine Transaction Processing) capabilities and a strong presence in the health care market. Although it was designed around the specialized MUMPS/M language, Caché happily talks Java and SQL.
In a similar move to its competitor Objectivy which launched the InfiniteGraph graph database, Intersystems has released recently Globals, a database implemented on top of MUMPS Global Persistent Variables — in fact InterSystems Caché, InterSystems Globals, and GT.M are all implemented on top of MUMPS.
Original title and link: Overview of the OODBMS World (NoSQL databases © myNoSQL)