Delphi and NoSQL
For Mongo, theres TMongoWire and pebongo (early stages). For couchDB, I believe one would interact mainly through HTTP/JSONFor Cassandra, I believe the best bet would be to somehow incorporate a supported language inside your Delphi app and use that to interact with Cassandra, or else implement a web service in a supported language and make it accessible to your Delphi application.
Hope it helps.
There is a new full featured driver for MongoDB "mongo-delphi-driver" which can be found (with examples) here: https://github.com/gerald-lindsly/mongo-delphi-driver.