We just had this amazing harp blowout here in Phoenix:

http://www.rhythmroom.com/event/640409-blues-harmonica-showcase-phoenix/

And watching the first series of players, it becomes very apparent that being able to sing really adds to the performance.

I figure you can learn just about anything on line nowadays. Do any of you have any suggestions or guidance for someone wanting to learn how to sing?

Check out New York Vocal Coaching and Eric Arceneaux on YoutTube and get thee to a teacher! You won't regret it. 

I have been working with Jeff Rolka-who I found on youtube and have been having a great experience!

Have you noticed Corey Harris' four-part lesson on singing?  I've never tried to sing before, and it has even me trying!