Are there any beaches in Boston worth a day trip? If not, what is the nearest quality beach? Thanks!

There's nothing in Boston. The nicest ones are at least 45min-1 hour away. Try Singing Beach in Manchester, Good Harbor in Gloucester or Pirate's Cove in Rye, NH.

Crane's Beach in Ipswich is also nice.

All superb choices - and you can also head the other way to Newport, RI for some great beaches - check out gonewport.com for listings and you can always enjoy the harbor and all the wharf area for eating/shopping afterwards.

YOu might try Revere Beach or Winthrop Beach both are pretty close. If you are taking the T, the blue line goes to Revere, and it's walking distance to the beach, figure 45 minutes from Boston. There are lots of local restaurants, pizza joints and the "World Famous Kelly's" for roast beef sandwiches and clam rolls, a legend in the Boston area.

Winthrop is a pretty little town, just north of Boston, and easy to find your way around. The beach is a little longer than a mile and very clean.
For Winthrop you would need a car public transit is not as easy.

Worth a day trip - depends on your perspective. If you live in Montana and have never seen the ocean, then definitely. For flat, cold water - as noted above - Manchester, Gloucester, Rockport, Ipswich. Only Singing Beach is easily accessible by public transportation. All get crowded if it is hot and parking costs a fortune.

If you want big waves and less crowds, you need to head to Cape Cod - but that is more like a 14 hour day trip - not my idea of a beach day.

If you just want to walk on a beach closer to Boston, then Revere and Winthrop are OK, but you will get very mixed reviews about whether or not it is safe to go into the water - much less polluted than years ago, but still not pristine.