Jez Cope, Chemistry IT Manager at University of Bath requests:
You asked me to email you details of the SSO system we use here at Bath: It's CAS (Central Authentication Service) from Jasig - http://www.jasig.org/cas
It's open source with a very well documented protocol and client libraries available in all sorts of languages, including PHP. It's also very widely deployed across the HE sector, so would be quite a good feature to add to LabTrove.