Dandelions may irritate you and your garden, but they have many health and medicinal properties. Dandelions are widespread, which makes them easy to forage. Of course, before you pick all of the dandelions out of your yard or a nearby park, be sure to find out if your foraging area has been sprayed with herbicides and pesticides. You definitely don't want to pick from a sprayed area. If you are unsure, ask your local park service. 
All the parts of a dandelion are edible and medicinal. It is very nutritious and is high in essential vitamins and minerals, helps with digestion, and is good for your liver. The flowers also serve as a great way to add pretty edible flowers to your dish, which look beautiful and nutritious. You can use the flowers to make a salve for sore mussels, joints, and dry skin. You can also make dandelion mead, vinegar, or tea.
Try using the leaves in salads, or sauté them much like you would with spinach by adding olive oil and garlic. You can also use dried and roasted roots to make a coffee substitute without caffeine, and it supports the health of your liver. The stem can also make for a cool straw in a drink. 
If you're interested in foraging for dandelions and want some interesting recipes, go to Grow Forage Cook Ferment. Colleen has a lot of fabulous ideas and so much knowledge to share.