Though i am not a believer of non standard stuff, but recently was asked this question on IRC on how to launch applications via a hyperlink, it was probably alright to do that in the users case, since this was for an Intranet and everyone had that software installed and were running windows.  The call:// link on skype gave me the idea that its got something to do with the windows registry (or atleast on the windows platform).

Found an article on MSDN that talks about this:

http://msdn2.microsoft.com/en-us/library/aa767914.aspx

About rp

Architect for large, highly scalable LAMP applications and Technical Manager with special focus on metrics based continuous improvement of teams and products. Rajat has close to a decade of experience of a very wide range of skills related to infrastructure, middleware, app servers all the way to front-end technologies and software development methodologies including agile, iterative waterfall, waterfall as well as ah-hoc startup using the right approach in the right context to reduce time to market.