I'm reading the book Seven Databases in Seven Weeks by Eric Redmond and Jim Wilson. The databases covered are PostgreSQL, Riak, HBase, MongoDB, CouchDB, Neo4J and Redis.
There are several Pharo/Squeak libraries for PostgreSQL:
HBase runs on JVM. It supports a RESTful HTTP API, Thrift, and a Java API. The first is probably the easiest way to write a Smalltalk interface.
Neo4J is a graph database. It is provides a RESTful API. I've not played with Neo4J, but I'd imagine the Smalltalk environment, and by extension any Smalltalk object persistence mechanism, make up a graph database. Probably speaking from ignorance here, but I'm not sure what interest a Smalltalk programmer will have in a graph database written in Java. :-)
Finally, there is Redis Client by Mike Hale and others.
I haven't finished the book, but so far I haven't seen any discussion on authentication or security of these HTTP-speaking NoSQL databases. If the database is lacking authentication or SSL, and if your threat model covers that, probably the easiest is to put these behind a proxy. And, for database and other such connectivity from the Smalltalk client, I suggest SpsSplitPasswordStore.