I had a few SameTime/Notes schools who were switching to Exchange 2007 and OCS 2007 ask me if there was a way to embed Office Communicator client inside of Outlook? The answer is yes. There sample add-on available here along with source.  Here is what it looks like:

Is there a Vista gadget for Exchange or Communicator? Yes, click here. Here is what the OC gadget looks like:

Here is the Exchange Web Services gadget where you can load calendar, inbox, tasks in a gadget. It will also pop up a side window when items are clicked:

Is there a way to get OCS within my Lotus Notes client while I am migrating to Exchange? Yes, there is sample Communicator add-on for Lotus Notes here. Here is what it looks like:

I hope this provides some information around additional options for connecting to OCS.