There's two ways you can go.

1. You can use a data provider like this: http://npgsql.projects.postgresql.org/exampleprograms.html
2. You can use a LINQ provider for Postgres similar to this: http://www.devart.com/dotconnect/linq.html?gclid=CP7V6ePG6ZsCFSMSagodlWxx5Q

Here's a code project article describing how to use the data provider: http://www.codeproject.com/KB/database/afppostgresqlintro.aspx

I have to use a webservice as data source, i make a wrapper for the webservices and put all the data in lists, so i can use linq with them. Then use all existing tutorials for MVC.