I have been given some summer snowdrop bulbs which still have the foliage on them. Can I plant them now, or dry them in the sun and plant them in autumn?
Snowdrops tend to dry out and should be planted out right away.
I would trim away some of the greens just to help in the planting, but leave as much of the greens that you can. The foliage dies away naturally and this feeds and give the bulb energy to store.
Here is an article with more information.