Here is an interesting article about the relevance and techniques for wardialing in 2014.
Wardialing and modems are still a reality despite the wide adoption of VoIP. Also, the available of VoIP at the war dialing tool side, has made this process more effective. Plus, the tools mentioned can be used for a lot of things other than war dialing, including nasty things like looking for second dial tone, IVR behaviors, etc. that can be used for other attacks.
I covered how to use tools like WarVOX for these attacks in my Hacking Exposed: UC and VoIP book: