Pat's Peak in Henniker, NH. It's about 10-15 min from Concord.
It's a small mountain, but being a beginner, you won't be able to ride the whole thing. It's relatively cheap and has a free learners area, a valley ticket option, and a full mountain ticket option. You can also choose half or full days for both the Valley and full mountain tickets, then upgrade the difference if you plan to stay the whole day. It's got a pretty decent park as well. Ben Ross (local pro) has a lot of build input there so it's top notch in build quality. I've always found it to be a fun place to ride.