Alexander Kuznetsov on SQLblog.com has an interesting series going entitled with Learning PostgreSQL. In the series he focuses on what it takes to move a SQL Server database and App to PostgreSQL and highlights some of the key differences between the two platforms that you should watch out for. I recommend it to any SQL Server developer planning to make the switch to PostgreSQL or any PostgreSQL consultant tasked with the job and not familiar with the intricacies of SQL Server.
His PostgreSQL feed can be found here here
So far on his list of articles in the series: