I second the nomination of the PA - undoubtedly the most versitile fly around, in either the "regular" or yellow configurations. If the brookies are a bit skitterish, as they were back in November, I'll drop down to a #18 or even a #20.
Another good one to try, as we drift towards summer, is the foam yellow stonefly - I noticed LRO was getting cleaned out of those last year. Finally, this time of year is perfect for a Mr Rapidan - a Wulff type fly with yellow posts that is very easy to see in choppy water.
Brook Fan: If you want to get one of those wild brookies, as George Allen used to say, the future is NOW (although this weekend isn't shaping up too good, weather-wise). There are a couple of streams in the park that don't require much hiking where you can get some specs - just don't expect any monsters. One day I would like to try Raven Fork; that stream does require quite a hike, but it is larger and therefore holds some larger fish. Many years from now, after the restoration is complete, Lynn Camp might be a similar fishery. If you would like, email me at email@example.com
if you would like some streams and locations, etc.
A living jewel