Fishing in the Black Hills is starting to get back to normal. Stream flows, for the most part, are dropping to more manageable levels throughout the hills, although Rapid Creek is still high (and unfishable) in most areas. Fishing within Rapid City is confined to slower stretches where you'll need to get down a bit deeper to find success. Don't mess with nymphs right now, just chuck streamers. You'll catch fish and won't have to worry as much about catching the junk on the bottom. Kreelex, articulated patterns (olive or black), and any other fly with movement should be a good choice for you.
Spearfish creek is one area of the hills where you can find some familiar flows and friendly, fishable waters. In the canyon and in town have been fishing great. You can use dries (terrestrials will be your best bet), and dry dropper rigs. The clear waters of the creek will require small flies, and a stealthy approach. Don't hesitate to use them both.
Castle has been fishing really well for some time now. Brookies and browns can be found on either end of Deerfield reservoir as long as you work slow and don't spook fish. Beetles patterns are a favorite of ours, but drop a jig style hares ear wet or hot spot PT for some bonus fish.
One of the real positive fishing stories has not been in the hills this spring, but instead out on the Missouri River in Pierre. It was a late arrival, but the white bass fishing has been lights out for well over a month. They are at the tail end of this frenzy now, but you can still find stretches of big schools, and consistent hook-ups with big feisty white bass. One of the funnest fish to fight in South Dakota, no question about it. Bring along chartreuse bully buggers, small clousers minnows, deceivers, and murdich minnows. The lighter the fly, the better your results will be. There is still some fun to be had, so get out there for a few days and fish in Laframboise causeway and along the north side of Laframboise island. It is starting to get green, so the clock is ticking!