Let's level with each other for a moment, can we? There isn't a lot in Delaware. Ranked 45th out of 50 in population, more than half the population lives in New Castle County near the I-95 super-corridor connecting Boston, New York City, Philadelphia, and Washington DC. Perhaps strangely, few rides actually exist in this section of the state. Blue Diamond Park was Delaware's first new build ride park in generations when it came there in 2003, but the rides were closed and sold almost 10 years ago now. Prior to that, New Castle County needs to go back until at least the early 1940s, when Deemer Beach Amusement Park had been rechristened "Deemer Beach Colored Beach" and was a segregated African-American establishment. Most other similar places had closed by the 1930s. This included Brandywine Springs and Shellpot.
So enough history: you want now. Now, as even 70 years ago, there is one place above all others in the state of Delaware to go for fun. That place is Rehoboth Beach. Conveniently located to the town of Lewes for those looking to march all the way up the coast, it is a summer resort community with tons of house rentals and cute motels as of yet not ruined by the encroachment of real estate speculation. Generally known as an inclusive and gay-friendly community, Rehoboth doesn't have the sheer number of attractions Wildwood or Ocean City NJ and MD have, but it does have some nice stuff. Funland doesn't seem like it should have anything notable at first glance, but look again, and you'll see this.
Constructed over a two year period before opening in 1978, almost entirely in-house, Funland's suspended dark ride Haunted Mansion frequently made the DAFE Top Ten. This is, without question, the shining jewel in the state and really the only significant reason for theme park fans to go. Funland's small list of attractions includes an arcade and a few flat/kiddie rides. There are other small parks in the area, but most of them concentrate on slide based attractions. Both Jungle Jim's and Midway Speedway Park have water slide complexes, but it's Jungle Jim's and their Cobra themed water coaster that is likely the one more worthy of inspection.
For those worried about finding parking, there's some more sedate water attractions elsewhere in the state: Killens Pond State Park has a small water park, and just north of Ocean City, MD in the Delaware town of Fenwick Island is Thunder Lagoon. And the biggest single attraction in the state is likely the state fair each year, with big steel brought in by Wade Shows.
There's one last item to review in Delaware, and that is of the seasonal haunt variety. Frightland in Middletown, DE creates an array of haunt walk throughs and hay rides, but also contracts with Houghton Enterprises to have a midway of amusement rides to go along with it.