here's a picture from earlier in the season

and one more picture

When I saw the first picture I thought of the Japanese Tree Lilac. Is this it?
http://www.hort.uconn.edu/plants/s/syrret/syrret1.html

No, definitely not a lilac. It doesn't show in the picture I uploaded, but there is a Japanese lilac right beside this mystery tree, and the shape, leaves, and flowers are all wrong. Also, the "flowers", if that's what they are, never opened more than what's in the first picture. They weren't fragrant, either. :(

It's an Elderberry (Sambucus sp.)

Your photos don't reflect enough unique characteristics to identify which species though.

The first to bloom in our area is the Red Elderberry, usually early to mid spring. The flowers are like the ones in your photo and not like the flat topped group of flowers seen on other species. The blooms of Red Elderberry have a strange and some would say unpleasant scent but only up very close. A nice shrub for shady woodland gardens and good for birds.

Mike

Thanks for the help. It's a nice tree, though mostly fruitless. The robins seem to like nesting in it though, which is good