MongoDB & CouchDB have a lot more history as open source project. Riak, being recently released into the wild, will have its various how-tos and documentation grow in time.
But lets say you wanted to do a blog in python, the client libs they provide are pretty well documented inline. Check it out: http://bitbucket.org/justin/riak/src/tip/client_lib/jiak.py
MongoDB & CouchDB have a lot more history as open source project. Riak, being recently released into the wild, will have its various how-tos and documentation grow in time.
But lets say you wanted to do a blog in python, the client libs they provide are pretty well documented inline. Check it out: http://bitbucket.org/justin/riak/src/tip/client_lib/jiak.py