rw wrote:

We live in Massachusetts and put down a corn gluten pre-emergent weed
control product back on March 19th.

Although the lawn is still dormant, we've noticed some type of weed has
emerged (March 27). Can anyone identify what type of weed it is (URL
to picture is below) and the best way to get rid of it / prevent them
going forward (organic if possible).

http://www.addieryan.com/2006/2006March_LawnWeed.JPG

Thanks, rw
looks an awful lot like a wild Easter Cactus but given your location I'd say
thats near impossible.
Eric