What we did this weekend
It was the first weekend of real spring, so we dug a few holes, got us some lumber, and built us some raised beds.
Putting the urban back in "urban gardening"
We used the dirt we dug up to line the edge of the yard - it's safe for growing flowers and maybe a protective hedgerow, but probably not anything edible. The raised beds are half full of layers of organic soil and mulch and whatnot, to be added to every year until we have nice deep soil without any broken glass or lead.
Next project: putting up some kind of a fence so people don't wander over into our yard and accidentally fall into the raised beds. It hasn't happened yet, but this is still Brooklyn, anything is possible!