Haha Mid-Atlantic parks are my forte. If you need any trip planning tips just ask me and I'm sure I'll be able to help.
As of now the only notable parks I have not been to in the Mid-Atlantic Region (Virginia to Pennsylvania to New York) are Six Flags America, Waldameer and Kennywood, and with my ankle surgery coming it doesn't look like I'll get them this year. Anyways the list of notable parks in this area are as follows.
New York:
-Luna Park (Coney Island): Go for the Cyclone.
-Rye Playland (Credit Nab): Go for the Dragon Coaster and 1 of 3 Derby Carousels IN THE WORLD. The town it resides in is also incredibly beautiful and it's just outside of the bustle of the New York Metro area.
New Jersey:
-Six Flags Great Adventure: The flagship park of the state, has 2 of the best credits for enthusiasts in El Toro and Nitro and is also the only park in the world with 5 B&M coasters.
-Morey's Piers: Simply put it's on one of the best boardwalks on the east coast. 3 Piers with a variety of rides and definitely a full day of things to do with 2 water parks on top of it. It's a hike to the beach though, so be prepared.
-Clementon Park: The oldest operating park in the state. With a recent buyout and new ownership, Clementon Park has made some moves recently that definitely put them back on the map in terms of being a place to visit. While Hellcat isn't in its prime anymore it's still a coaster to check out for what is probably the most intense twister section in the US.
-Casino Pier: Great day trip place. Not as large as Morey's Piers but has a good selection of rides. Watch out for the prices as it can get a little expensive if you plan to spend more than 2-3 hours there.
-Jenkinson's Boardwalk: Read Casino Pier again. They also have an aquarium!
-Steel Pier: Read Casino Pier AGAIN. Also Atlantic City is a hole, so visit in the daytime/evening and get out.
-Ocean City: Read Casino Pier. Gets mobbed to all hell with tourists from Philly and New York in the summertime so be prepared for large crowds.
-Keansburg: Small park on the Northern end of New Jersey, very similar to Clementon Park in terms of size.
-Bowcraft Playland: An even smaller park and further north than Keansburg. They only have one notable ride in the Crossbow, so it'll only really be a stopgap park at best.
Pennsylvania:
-Hersheypark: One of the oddest 'major' parks in the country. With a tight footprint the Comet Hollow is one of the best places to get roller coaster credits and spans the ages from old-time classics (Comet & SooperDooperLooper) to the modern day thrill machines (Skyrush & Great Bear). While their operations can be questionable at times and their rides are notoriously short in length, Hershey is definitely a park that can grow on you over multiple visits.
-Dorney Park: The only park in the world with three different inverted coasters, and one of the most historically significant on top of it. It's great to visit during the weekdays for marathon riding, and also has one of the best haunts in the Northeast in the fall. While Dorney seems rather small rides like Talon, Steel Force, and Hydra definitely place it as one of the best parks in the region.
-Knoebel's (Must-go for any sane enthusiast): If you want to see a typical themepark turned on its head this is the place to go. Located at the foot of the Appalachian Mountains in Central PA Knoebels is one of a small collection of parks that has free admission and parking. Your admission comes in the form of tickets, which are still incredibly cheap ($40 worth can easily get you by a full day). The food is great and also cheap compared to other major amusement parks, and there's also a sit in restaurant if you feel like it. Classic rides like the Flying Scooters, Tumbler, Phoenix, an Authentic Haunted Mansion, and one of the best Log Flumes not named Dudley Do Right's in the country. This park is any old school enthusiast's dream park, and definitely worth the mountain trek to.
-Kennywood: Right outside of Pittsburgh is another old-school park with its own take on rides. Kennywood has its fair share of old-school coasters and flat rides. It has 3 of the oldest operating wooden coasters in the country, each with their own kick. Kennywood is also home to a Morgan rehash coaster which has a near 230 foot drop down a hill and UNDER another coaster into an ending rivaling Nitro in air time.
-Waldameer: located near Lake Erie, this is a small park with one of the best wooden coasters in the country. They also have a nice collection of flat rides along with one of the best drop towers around.
Maryland & Virginia:
-Six Flags America: Right off the 495 Beltway and sandwiched between Baltimore and Washington DC,
read this thread.
-KD
-BGW
Not too far from this region you have Cedar Point, Kings Island, Dollywood, and Carowinds, which are really the only notable parks in their respective states. Cedar Point and Kings Island are great credit grab parks, and have their fair share of good coasters. Dollywood is a little off the beaten path but the experience that can be had is definitely worth the trip alone, the coasters are just a bonus. Carowinds is basically a 'clone' of Kings Dominion and is really only worth the trip for credits and Afterburn, one of the best B&M inverts out there.