How do you use pip, virtualenv and Fabric to handle deployment?

What are your settings, your tricks, and above all, your workflow?

These tools are great but there are still no best practices attached to their usage, so I don't know what is the most efficient way to use them.

• Do you use pip bundles or always download?
• Do you set up Apache/Cherokee/MySQL by hand or do you have a script for that?
• Do you put everything in virtualenv and use --no-site-packages?
• Do you use one virtualenv for several projects?
• What do you use Fabric for (which part of your deployment do you script)?
• Do you put your Fabric scripts on the client or the server?
• How do you handle database and media file migration?
• Do you ever need a build tool such as SCons?
• What are the steps of your deployment? How often do you perform each of them?
• etc.