Bernadette Teaches Music YouTube Channel   This YouTube channel has lots of step-by-step instructional videos for many strumming techniques and songs  

Little Kids Rock-Ukulele   Little Kids Rock is a website with many instructional videos as well as song sheets for current radio pop songs

Dylan Layne YouTube  Dylan Layne's YouTube channel teaches lots of Contemporary Christian hits.

Acoustic Bridge  This website has a huge list of 4-chord songs as well as tutorial videos for each.  It also has a nice buyer's guide to help you decide which instrument to purchase.