The Giver's Log (Has super cute and unique ideas for 13oz or less packages to send)
and of course, Sunny Jane's blog, since she is the one who started me out on this idea!
Basically, Happy Mail is all about sending someone else a bit of happiness! And I thought "What could be happier than cupcakes?!" Thus, Cupcake-Party-in-a-Box became my first packages to send out.