iFreeTools CRM (alpha) - the CRM for Google AppEngine, is now listed on Google App Engine's Application Gallery
Customized solutions over iFreeTools CRM can also be deployed to your sub-domain (like say, http://crm.yourdomain.com).
Such a deployment enables 2000 emails/day and 1GB of storage. Additional capacity can be purchased directly from Google.
For more details on custom deployment options, refer to : http://crm.ifreetools.com/about