Check Skype SIP Beta http://www.skype.com/business/form/sip-beta/
Don't expect to be up and running quick though.
I have read also that Skype may have to change technology because of legal battle over who owns the tech. Maybe they will be all SIP in the future?
I tried to pilot this with Skype in June and clearly weren't ready then. They were still in the certification phase. Even after certification, they weren't ready for the Enterprise.
I am looking for documentation on how to setup the Skype for SIP to Cisco UCM SIP Trunk. There is a dedicated document for Cisco's UC500 but nothing for UCM. I signed up for the open beta and have the Skype for SIP details, but cannot seem to get the SIP Trunk I configure on the UCM side to connect to Skype's SIP gateway.