Art in the Garden, Vinal Ave., Somerville--The best for ages 5-9.
Arlington Boys and Girls Club--themed weeks have a little educational content.
Arlington Center for the Arts--Drama camp was good.
Major League Soccer Camps--just mornings (1 week), lots of fun.
Somerville Youth Camp (at an elementary school)--only so-so (sorry).
Somerville Recreation Department, Lacrosse Camp--pretty fun for my 13 year old last summer.
Museum of Science camp--always looks good, but pricey and good things fill up.