https://github.com/zdavatz/odba
ODBA is an Object Database Access Library written in Ruby. ODBA serializes/marshalls your Data (like DRb does as well) and stores the data in your Database. With ODBA you can access your data in your database directly with Ruby, no SQL needed.
Also, ODBA manages your Cache. Not like ActiveRecord, ODBA stores the most frequently accessed data in your computers memory and once in a while make an SQL query to fetch the marshalled data out of the DB and store it in the cache.
https://github.com/grauwoelfchen/shoe
Use shoe to testdrive ODBA in a small application.