Anyway, up until now I've only learned how to strum with my index finger but I ran across this video today, which is educational if slow paced. If you go to the beginning, he also shows how to make a couple common ukulele chords in pretty painstaking detail.
I've been trying to practice thumb strumming tonight. It's a little frustrating when I'm used to using my index finger, I'm having trouble not making a loud click on the upstroke and it makes me distracted by what my right hand is doing more than normal, but I like that it makes a different sound for variety. I also like that it coddles my index finger, which I've banged up a little in my excessively enthusiastic strums.
There's a metric crapton of ukulele tutorial videos out there because of how trendy it is now*, but many of them don't seem to be that useful. I'll try to link the ones I like here.
The first instructional strumming video I watched was this one but I got about a minute into it and ended up just being like this :-o and deciding to ignore it until I had more skills. It's a great video though. If you are some kind of wizard.
* which is probably the only reason I'm playing it too, I'm a trend follower!