Middlesex County Message Board: If you have a single query that you want posted to a semi-permanent "bulletin board" type message facility, I suggest you use the RootsWeb Middlesex county message boards. This list is "gated" to the MAMiddle List so your "one-time" message will also appear there.
Middlesex County Mailing List : If you have a serious interest in Lexington genealogy, or genealogy within Middlesex County, I strongly suggest signing up the the Middlesex County Mailing list to be part of the email exchanges of other county researchers. Click the link and enter subscribe in the subject title and in the message of the email.
Cyndi's List (Massachusetts listings) - Web site includes thousands of genealogical related web sites.
LIBRARIES & MUSEUMS:
Revolutionary War Pension Records & Bounty Land Warrant Application Files - index of microfilm information at LDS
Probate and Family Court Department