Yeah, don't eat the furry fiddle heads. They contain a carcinogen. Won't kill you (I mistakenly ate years ago) but not the true fiddlehead you want to eat.
The book Northeast Foraging by Leda Meredith and Stalking the Wild Asparagus and Stalking the Blue-Eyed Scallop by Euell Gibbons are three books I use for reference.
Right now one of the most abundant forage greens is Garlic Mustard, you'll see it along the sides of roads everywhere. The plants are about 12-14" tall today and should be perfect for harvesting. Lots of recipes online. Also in season is Japanese Knot Weed. Its that green fast growing bamboo looking stuff. Never tried it but you can read online about its uses ans suitability for forage. Along the ocean one of my favorites is sea rocket. Its a succulent, dark green and leaves resemble the shape of rocket or arugula. Seabeans are good, they grow in the tidal zone and look like mini asparagus. Salty but tasty. The early leaves of the Linden trees can be eaten but I've never tried. In a few weeks the black locus will bloom and I'm told the white flowers are edible. Dandelion greens are widely foraged and easy to identify. Note of caution, take care with where you forage. For instance, rail beds / train tracks are notorious polluted, I would take anything close to them. Use common sense when foraging.
Getting into foraging makes fishing all the more enjoyable as you can get more deeply connected with the surroundings and have a little snack while at it!
Definitely get a good basic foraging book though, will save you time. Northeast Foraging is a great pictorial one to pack along. The other two read more like non fiction and are less easy to use as a field guide.