I was checking out the UC Developer Portal recently and It seems it is not up to date on the available Virtual Labs for UC Developers, as it only list 5.
For a more up to date list, you can visit this URL:http://msevents.microsoft.com/CUI/AdvancedSearch.aspx?culture=en-US#culture=en-US;advanced=true;sortKey=;sortOrder=;pageEvent=false;startDate=7/21/2008;endDate=12/31/2008;kwdAny=;countryId=US;languageCode=en;audience=2;products=170;eventType=4;searchcontrol=yes;s=1
It looks like these Vitual Labs cover the UC AJAX and Communicator Automation in depth. I think there is one lab on UCMA, but there doesn’t appear to be one on the UC Client API. Overall very good materal and if you are new to using any of these APIs, take the time and go through the labs, best of all they are free to use.