post_json

What I did: 1) Use the latest Postgres (9.3) 2) use Rails4 - this provides String/Integer Arrays, HStore, UUIDs out of the box 3) use post_json (https://github.com/webnuts/post_json). These tools made it simpler to do things like tagging, user-defined data attributes, hierarchical data, flexible configuration data. It was always possible to store much of this data using text fields and JSON.parse (or some such), but the new Postgres stuff makes the flexible datatypes queryable. And as built-in support for flexible data types comes online, you can throw away your custom serializers. There's other Postgres datatypes that I haven't used - for geocoding/geosearching, network addresses, etc.

If you're looking to try Postgres as a full on document store there's more and more tooling around making this feasible. Here's one newer gem that makes it pretty straightforward for Rails: https://github.com/webnuts/post_json