I agree with all of the many good views in the Hudson Highlands that have already been mentioned in this thread and the one at AdkHighPeak. I will just add a few more: The "Pitching Point" on the Howell Trail on the north ridge of the Crow's Nest. The other Sugarloaf Hill south of Garrison. And a few lowland views at the Little Stony Point below Bull Hill (Mt Taurus), the Bear Mountain Bridge walkway, Manitou Point, and the lawn at Boscobel.
Trophy Point at West Point also offers a great view. The visitation rules at West Point are far more stringent in recent years, and I am not up on all of the specifics.
This is a rather long gallery from the recently opened
Walkway over the Hudson in Poughkeepsie. The walkway on the
Mid Hudson Bridge also offers good views. There is a good view
down onto the bridge from the adjacent Franny Reese State Park. That view has been greatly cleared and improved since I took the several photos that appears in this gallery. The trails throughout the Franny Reese park were similarly improved since my last visit, and perhaps they have reopened some of the former Hudson River views along the carriage roads of the Cedar Glen estate of Dr. Charles H. Roberts.
In Staatsburg the hiking trail along the Hudson River between the Mills Mansion and the camping/cabin area at Norrie Point. There is an excellent view of the
Mount St. Alphonsus monastery from the cabin area along the trail that is well worth finding. I tagged that photo onto a photo gallery from the Vanderbilt Mansion historic site in Hyde Park where there are several views of the Hudson such as
this one which also features the Mount St. Alphonsus monastery.
I agree with Tom's suggestion of the
Ferncliff fire tower where the view is awesome. I also agree with the the previously mentioned views at Poet's Walk and Olana (both the south lawn and the viewpoint over the Rip Van Winkle Bridge along a carriage road). There are also similar views at the Montgomery Place and Clermont historic sites.
Saugerties Lighthouse Trail. It is worth checking the tide tables at the start of the trail or via their
website. Those tide tables are also good for the trail to Cruger Island where there are also views on the Hudson, access from a Tivoli Bays parking area which is down the hill from Bard College. The Hudson River tides have been rather low during this relatively dry summer of 2010 and not much of an issue (of course YMMV depending on the phase of the moon and rainfall).
In addition to Overlook some of my favorite Hudson views from the Catskills are from the Palenville Overlook, Huckleberry Point, the many views from Boulder Rock to North Point at the North Lake State Park (all are good), and Milt's Lookout north of Stoppel Point.