New York City:
596 Acres is a nonprofit that connects NYC residents to the land resources around them; they’ve created a helpful map where NYCers can find vacant city-owned lots close to their homes.
Here’s a fun infographic (link to PDF) that explains how to get to work on a vacant lot in New York City:
(image source: 596acres.org)
Baltimore:
The City of Baltimore has made the process of finding a vacant lot in your neighborhood easier than ever with its Power in Dirt initiative.
Power in Dirt has compiled a spreadsheet of all the city-owned vacant lots that are available for adoption (the spreadsheet has recently been updated and turned out a little wonky, but it still should be usable.). To adopt a lot, simply fill out and submit this online form.
If you wish, the city will provide access to water to the lot for a fixed rate of $120.00 per garden season (March 1 through November 30).
**UPDATE**: check out our Baltimore City-owned vacant lot Google Map! New lots are being added every day!