People are starting to catch on to two very powerful ideas - that functional languages are ideal for building persistent storage repositories, and that a huge subset of web applications don't need a relational data model.
Several of the more interesting solutions I've come across:
- CouchDb is a document oriented database accessible via an HTTP REST protocol, and supporting a formula language for generating "virtual tables" from raw content data. I'm not yet sure what I think of this document oriented development model, but it's worth further consideration.
CouchDb is implemented in Erlang. I'm not 100% sure about Depot, but I have a strong suspicion that it's Haskell. Many people consider these to be fringe languages, but there are strong reasons for their growing popularity in this space.