Jeff Potts, a lead architect at Optaros, Inc has written a Tutorial on Getting Started with CMIS.  I would highly recommend this as reading for anyone who wants to get hands on experience experimenting with CMIS.  In this tutorial Jeff:

• Gives a brief summary of the CMIS Spec
• Walks the user through setting up a CMIS repository
• Walks the user through exercises performing various common operations against the repository.
• Points the reader to additional resources