I tried to search in PlantFiles for shrubs/trees with winter berries but it doesn't seem possible ... unfortunately I didn't get a picture of them ... these are small trees/large bushes with prolific red berries in January in Maine ... the berries hang down in multiples like cherries and I was thinking maybe chokecherry but the berries are configured differently ... they hang down on single stems but in bunches ... any ideas?
But just in case that's not it... I did a search using Horticopia and it narrowed the genera down to very few choices. I omitted a few more options knowing that the fruits are clustered. The possible plants (as far as I can tell) are:
Aronia (probably A. arbutifolia)
Crataegus (probably C. phaenopyrum)
Malus (gazillions of different species)
Viburnum opulus (clearly not a sterile one)
You didn't say whether your question pertains to cultivated specimens of plants, or individuals occurring in native situations. That would help narrow the field.
Examine the bud/twig/branch arrangement (if you can't provide a picture!). If it is oppositely arranged, then it is most likely a viburnum. The rest of plantfreak's list is all alternately arranged actors.
It would most likely be Viburnum trilobum which is listed here and elsewhere as Viburnum opulus var. american or some such heresy. Aronia arbutifolia wouldn't be confused with a tree, being a shrubby colonizer.
Otherwise, the more tree-like from the list above are the Sorbus (most likely Sorbus americana in Maine) and Crataegus. These are good candidates for native situations. The Malus is also tree-like, but would most likely only be found in cultivated sites.
It is cultivated -- planted deliberately outside a hospital ... and I'm no longer there to examine the twigs, unfortunately ... I just remember the whole thing had a very dark appearance, not an orangey-red berry ...