I found this EXCELLENT tumblr recently that is all about Happy stuff. ^_^ I *HIGHLY APPROVE*
There are far too many awesome things there to link to them all, but I'll share some highlights.
Here's a cute stop-motion video: Show/Hide
The rest are links to pictures.
Yes We Can
I Love You
What I want to be
Happy Existence Day
Life is too short
And finally, here's one that isn't necessarily about being happy, but it did make me smile. ^_^ Here.