Cisco clean access is part of the Cisco NAC solution Clean Access is the appliance based solution.

However to implement Cisco NAC architectural framework you can implement this without purchasing a dedicated appliance you can use an existing router that is running an appropriate version of IOS software and the cisco ACS (Access control Server) (as well as the appropriate Cisco Trust and possibly security agent on the client side). These can intergrate with vendor policy servers to provide a policy compliance validation at network access.
i.e is AV installed, is it up-to-date is patching up-to-date etc.

I think the clean access and NAC architectural solutions provide similar functionality however you may be able to save yourself some expense if you go the Architectural framework route as you do no need a dedicated appliance.

Information on the NAC architectural framework is available here:
http://www.cisco.com/en/US/netsol/ns...s_package.html
http://www.cisco.com/en/US/netsol/ns...080270825.html

I had a good document at work about deploying the Cisco NAC however I can't locate it on the net and the link from the release notes is not working.

I am also heading up a project to invistagate NAC for our environment we are just starting to set up a test sandpit, hopefully that will be up and running soon.