Stoneham Municipal Employees FCU is offering a special 5.85% APY 7-month certificate of deposit. The minimum deposit is $5,000, and it requires new money. There's also a special 5.01% APY 5-month CD with a $1,000 minimum deposit.
In addition to employees of Stoneham Township and a few other MA townships, membership is open to members of the "Friends of the Stoneham Public Library." Please refer to the credit union's membership page for more details. According to the The Friends website, membership into The Friends is open to all. The cost of membership is $10. Membership into the credit union requires a minimum deposit of $5 into the regular share savings account.
Branches are located in Stoneham and Wilmington, Massachusetts. The credit union is federally insured by the NCUA (Charter # 15393). It's a small credit union with $21.1 million in assets and 3,266 members so I doubt they'll be able to keep this special too long if they get a lot of demand.