What is RavenDB?
RavenDB is document based (NOSQL) database written in C# for .Net framework. RavenDB nicely fills the data storage niche where RDBS systems are inflexible to meet needs of real world. Because RavenDB stores schema-less documents the flexibility and speed of development is unmatched by RDBS. RavenDB is also Open Source project and the source is available at the http://ravendb.net.

Some of RavenDB features:

Scalable infrastructure: Raven builds on top of existing, proven and scalable infrastructure
Simple Windows configuration: Raven is simple to setup and run on windows as either a service or IIS7 website
Transactional: Raven support System.Transaction with ACID transactions. If you put data in it, that data is going to stay there
Map/Reduce: Easily define map/reduce indexes with Linq queries
.NET Client API: Raven comes with a fully functional .NET client API which implements Unit of Work and much more
RESTful: Raven is built around a RESTful API
Cloud: Runs in the Azure and other cloud platforms

What is RavenDB notification plugin?
RavenDB Notification plugin enables you to receive notification from the RavenDB Server about Put and Delete actions on the specific document types. Currently plugin supports 3 types of notifications:

PutId – will notify client with the Key of inserted document.
Delete – will notify client with the Key of deleted document.
Put – will notify client with the key of inserted document and the document itself. Be warn that this functionality can generate lots of network traffic.
Client is able to subscribe / unsubscribe to each notification on document type basis.

Check my blog on how to use this plugin: 

Cheers