Lilac Sunday at the Arnold Arboretum (in Jamaica Plain) is an event I’ve attended consistently since I was a kid. I printed their t-shirts last year, one of my favorite projects, and just found out the design contest for next year (2011!) is already under way. So I encourage you or any designer friends you have to make a submission or three. Full details can found at the Arnold Arboretum Lilac T-Shirt Contest website.