One of my favorite (if slightly overdone) lounge bars in the area is Om, right here in Harvard Square. On weeknights, the 5-for-5 deal is quite good, plus the smaller crowds allow for more one-on-one time with the bartender. On a particular Wednesday night we spent the early evening grilling the poor man about how he blends each cocktail. Apparently they make their own simple syrup and always use fresh fruit for all their mixes.
My usual drink is the Lavender Cosmo. It's light and fruity, made with fresh blackberries and a champagne float, then finished with a spritz of lavender essence. It's pretty and perfect, going well with a plate of the housemade momos (one of the best bar bites around!)
Be forewarned, on weekends this place becomes a pounding night club minus the dancing. You'll have to shout across the table to hear your date, so take your drinks out to the small beer garden in back or just have dinner on the sidewalk patio instead.
57 JFK Street
Cambridge, MA 02138