Redis is a popular choice. What you're after is a database driver that doesn't block.
The databases you listed are all very different. Redis takes the idea of key-value storages and runs with it, adding a variety of data types and ways of querying data. People often note that redis scales down very well too; meaning that it has very low overhead despite having the ability to perform.
Here is a list of available database modules: http://wiki.github.com/ry/node/modules#database
