This little gem is Bulbocodium vernum which appears, seemingly overnight, in the spring. There is no foliage to warn you that they're coming, just flowers that appear right at ground level where there was nothing the day before. It is also called Spring Meadow Saffron. They are closer in appearance to a miniature Colchicum than a crocus, though all are at least distantly related. These will grow in full sun or partial shade, but we have ours in full sun in a rock garden type setting in well drained soil and they seem to be happy. Happy plants are a good thing. They will multiply freely if you have them in the right place. If you get too many in one spot (not likely at this time of year), simply dig some up and move them, replanting immediately so the bulbs don't dry out.
Although this little gem has been in commerce since at least the early 1800s it seems to be much more common in Europe than here. It's native habitat is an Alpine meadow and it is found in the wild from the Pyrenees to the Carpathians. It is good down to zone 3.
Although not as cheap as crocus bulbs and a bit less formal looking (downright disheveled sometimes), they are well worth growing as they bloom before most of the crocus we have growing here and anything that blooms really early after a crappy winter is most welcome to live in my garden.