Here is all the important links for the stitches project:

• SVN Commit Access
• SVN Readonly Access
• JIRA for Stitches
• Forums for Stitches
• Stitches Demo [The Server] [The Client]
• Commercial Support
• Continuous Integration Server

If you have installed the stitches plugin, you will be able to access the wsdl here.
 
While this is not a link, it's "kind of" because you are using a URL to the svn repository:
To checkout the plugin:
svn checkout  https://svn.codehaus.org/grails-plugins/grails-stitches/trunk/ grails-stitches
To checkout the client example:
svn checkout https://stitches.googlecode.com/svn/trunk/stitches-client stitches-client