I know it's super late, but here's the Sprayground/Wading Pool map all updated for 2010.
The Wright Park sprayground is a work in progress, and Franklin's update should take place this year. Hopefully, a new sprayground will open there next fall and there won't be any gap between wading pool removal and sprayground installation as there was at Wright.
Update: The official name is "Gas Station Park" - more on this later.
OK, it's not really a mystery park, but that's what it seemed like when we ran into this bright blue cookie-moster colored park yesterday. Turns out, it was converted from an old gas station through the Health Department's "Brownfields" project and is now being transformed into a playground by the South End Neighborhood Council.