MongoDB: Ignoring extra elements on mapped classes (I had problems with this using MongoDB)
MongoDB: Read preference and write concern suitable for a replica set
MongoDB: MongoFileSystem - An implementation of IFileSystem for MongoDB

MongoDB is a great database choice for n2cms. MongoDB can be used in a
replica set with three or more members to provide redundancy (High
availability) and maybe also for scaling read operations on more
database server instances. When using MongoDB replica set it is very
likely you need more n2cms web servers as well. The MongoFileSystem
stores the files in the MongoDB so they are automatically available on
all web servers. A special HttpHandler for serving the files with decent
cache settings is also included. My favorite setup is three servers,
each one with a n2cms web server and MongoDB replica set member locally.
This way high availability can be achieved if you use some DNS failover
feature.

Configuration example:
<connectionStrings>
<add name="N2CMS" connectionString="mongodb://localhost" />
</connectionStrings>
...
<database connectionStringName="N2CMS" caching="false" flavour="MongoDB"
tablePrefix="n2">
<files storageLocation="Database"/>
</database>