Today was the first day I've been able to poke around Westborough WMA's ragweed fields for Connecticut Warblers, and I managed to kick up one bird in the infamous 'stone pile' field. Historically this field has produced these birds "reliably", and also hosted the Harris's Sparrow a few years back.
As a refresher, please note the Connecticut Warblers seem to like pumpkin and squash fields overgrown with ragweed. They often work the edges of said fields, and can be located as they flush (almost underfoot at times!) and perch in the edges, particularly in sumac. The link below shows a Google Earth photo with the three best ragweed fields labled. Please also note that the birds use cornfield edges as well. I've yet to make it over to the entrance along route 135 (it is listed as Wayne F. Maccallum WMA over there), but this side also can host the birds in numbers.