I have picked and used the following 8 plants. I'm in the Northeast, but I believe most of these are found throughout the US.
Most of these are best picked in the early Spring/mid-Spring.
1. Dandelions are the quintessential spring foraging plant, with edible and medicinal flowers, leaves, and roots. They are super easy to identify, and any look-a-likes are edible and medicinal as well, so no worries there.

Make dandelion salve with the flowers, dandelion pesto with the leaves, and dandelion root coffee with the roots.

If you’re worried about harvesting dandelion blossoms in the spring because they might be food for bees, it’s actually not as big of a problem as it’s been made out to be.
2. Chickweed is a tasty edible green that comes up in early spring. In some milder locations it will even grow throughout winter.

Once it warms up chickweed will die back, so be sure to get it while you can so that you can add it to salads or make chickweed pesto.
3. Wild violets and their leaves are both edible and medicinal. They come up in early spring and are often the first flowers of the season, making them a lovely sight.

They love cooler temperatures and will grow through the winter in warmer locations.

Make violet flower infused vinegar, wild violet soap, or violet leaf balm with your foraged violets.
4. Red or white clover blossoms are sweet and edible, perfect for adding to baked goods or infusing into honey. Red clover is especially high in vitamins and minerals and makes a wonderful tea.
5. Cattail are known as the ultimate survival plant, as every part of the plant can be used in some way. The young shoots that come up in the spring are the tastiest part, resembling the flavor of a cucumber, and can be eaten raw.

The yellow pollen that covers the flower spike in late spring or early summer makes a delicious foraged flour substitute.

Make fermented cattail shoots or cattail pollen pasta.
6. Stinging nettle is one of my favorite plants to forage for in the springtime. They are usually pretty easy to find, but don’t forget to bring a pair of gloves for harvesting!

Nettle is a superfood that is packed full of vitamins and minerals. Cooking the plant will dispel its sting.
7. Plantain is both edible and medicinal, and is a very important herb to know about. There are two main varieties, broadleaf plantain (Plantago major) or narrowleaf plantain (Plantago lanceolata), and both are beneficial.

Young and tender plantain leaves can be eaten raw and are highly nutritious. Older leaves can be added to soups and stews.

Using plantain medicinally is as simple as chewing up a leaf and putting it on a bug bite, bee sting, or minor wound. It stops itchiness and helps to heal wounds. Plantain is also a great herb to use in an herbal salve.
8. Cleavers is a plant that often surprises people with its medicinal properties! It is most well known for its habit of being a pesky garden weed and sticking to everything.

Turns out that cleavers is highly nutritious and is good for the lymphatic system. It is edible, but I recommend blanching first to dispel the sticky hairs.