The DPW will collect Christmas trees (the real ones, that is) for the first two recycling days in January - put your denuded, de-ornamented tree at the curb by 7 a.m. on your recycling day.
No word on Festivus poles, although since those are simply alumninum, you can presumably just toss them in your recycling bin. But should you? William Ricker posits that you should just put it away somewhere for reuse next year. Ward 7 Somerville, however, counters that "fresh grievances merit a fresh pole."