It must be a bad week now that Robert McCloskey's passed on too. He's always been one of my favorite authors, and between Make Way for Ducklings (which I own in both English and Spanish versions; if anyone knows of a Latin edition I'd buy it) and his wonderful Maine books (Blueberries for Sal, One Morning in Maine, Time of Wonder) I have such a hard time choosing a favorite.
My favorite duck crossing is not in Boston, though -- it's the one on Union Boulevard in Lakewood (south of 6th Ave). I'd always seen the signs on Union but had never seen the ducks until MileHiCon 1999, when I took a walk down Union and spotted the wonderful little ponds where they hang out. I highly recommend walking from 6th to Alameda along Union to anyone in the Denver area. Ducks make me happy.