I always wanted the functionality of select and call a number with Office Communicator from any window. I found an application that exactly does that. It is similar to Skype plugin for Internet Explorer and Firefox as shown here.
The German company ESTOS has developed this ‘helper’ for Office Communicator.
After you install this application, it assigns a default Windows Hotkey F8 for all applications. So when you are reading a mail in your Outlook, and you want to call a number that was listed in there, just select/highlight the number and press F8. The number will be dialled with Office Communicator. You can customise this Hotkey at anytime from Options window.
If the selected text contains a phone number, a phone conversation is started. If the text contains a Sip address (an @ in the text), an instant message conversation is started.
Download this useful application from ESTOS website in your localised language.