Canada’s Yellow Pages Group has formed a deal with Marchex to power click-to-call links throughout the Web. That last part is important — this isn’t click-to-call on YPG properties, but active wherever its advertisers’ numbers show up online.

This results from Marchex’s partnership with Skype, which brings that click-to-call capability to the table. For Skype users who have its toolbar installed, these numbers are linked to make a quick call, wherever they show up online.

From the release:

This agreement now makes it simpler than ever for Skype users to connect − for free − with the business of their choice through this growing communications channel.

This offering will allow users of Skype for Windows with the Skype Toolbar plug-in enabled to make unlimited free calls to approximately 370,000 businesses advertising with YPG with one simple click.

Businesses advertising with YPG will enjoy increased visibility as their contact phone number will be automatically highlighted where it appears on the Internet. YPG will be providing this offering to all of its advertisers free of charge.

Normally Skype calls to real phone numbers require a paid subscription. But in this case, the calls are essentially underwritten by someone like YPG to drive more calls to its advertisers. Returns come in the form of either pay-per-call, or clearer ROI it can show advertisers, via call analytics.

Last time we spoke with Skype, Marchex and other publishers trialing this, it was clear that these free call links were being clicked at a much greater rate (specifics undisclosed) than normal Skype links. This comes across in the form of explicit “free call” buttons for paid advertisers.

It’s a clever use of Skype and a way to tap into its nearly 600 million global users (one of the few tech products that boast higher usage than Facebook). This is also similar to what Skype has already done with European Directories, a story we broke about two years ago.

Soon after that, Marchex got on board with Skype to boost the utility of its existing pay-per-call products. It’s a powerful combination and we’ll see more directories sign up during a time when increasing competition from things like Groupon are making clearer ROI a survival imperative.