Data Warehouse and Django

Here are some cool Open Source tools I used recently:

• Kettle - great ETL tool, you can use this to extract the data from your operational database into your warehouse. Supports any database with a JDBC driver and makes it very easy to build e.g. a star schema.
• Saiku - nice Web 2.0 frontend built on Pentaho Mondrian (MDX implementation). This allows your users to easily build complex aggregation queries (think Pivot table in Excel), and the Mondrian layer provides caching etc. to make things go fast. Try the demo here.

My answer does not necessarily apply to data warehousing. In your case I see the possibility to implement a NoSQL database solution alongside an OLTP relational storage, which in this case is PostgreSQL.

Why consider NoSQL? In addition to the obvious scalability benefits, NoSQL offer a number of advantages that probably will apply to your scenario. For instance, the flexibility of having records with different sets of fields, and key-based access.

Since you're still in "trial" stage you might find it easier to decide for a NoSQL database solution depending on your hosting provider. For instance AWS have SimpleDB, Google App Engine provide their own DataStore, etc. However there are plenty of other NoSQL solutions you can go for that have nice Python bindings.