By default URLs are not clickable in Communicator. However you can apply the following registry tweak to make them clickable and launch them in your default browser.
Steps are as follows:
1. Open registry editor and go to the following registry entry:
2. Add the following key to above mentioned entry
(Type:DWORD), value can be either 0 (URL will appear as plain text) or 1 (makes URL clickable)
Now close the registry editor and restart Microsoft Office Communicator 2007, URLs should now be clickable. Administrators can control values of this feature via group policy settings.