Just in case you haven't seen the posts by Ed York and Michael Bogobowicz on Workflow Studio recently I wanted to call them out. In addition to providing some excellent activities and workflows for you, there are posts that explain the process of creating activities and workflows around XenApp, Provisioning Server, and SQL.

Michael wrote a workflow that automates the update of vDisks in Provisioning Server using the CLI tools:
http://community.citrix.com/display/wf/PVS+Automatic+vDisk+Update+Script

Ed has written up two excellent blog series on Workflow Studio:

• Workflow Studio SDK - This first series of posts detail Ed's experiences using the Workflow Studio SDK to build and debug custom activities and are an excellent place to start if you want to build your own activities:
  http://community.citrix.com/x/YIUJB
  Ed followed this series up with a post on building an activity to get a list of applications from XenApp using the MFCOM SDK and this activity and source code are available for download:
  http://community.citrix.com/x/KgE-B
  Ed also wrote a couple of activities that work with SQL Server:
  http://community.citrix.com/x/2IJiB

• Automating Workflow Studio - The second series of posts is on automating workflows. Ed has posts that explain how to use the PowerShell interface to start a workflow and pass parameters to it. He then goes on to explain how to build your own front-end for starting these workflows:
  http://community.citrix.com/x/ToNiB

As a reminder, all community posts on activity libraries and workflows will show up right in the Workflow Studio product under the Community tab so you don't even have to go out to the site to look. RSS feeds are also available on the Community site if you want to get notified in your favorite RSS reader.