Here's a little project to kill a few minutes on a wet afternoon (in my case, a Bank Holiday). A good one for young kids too, because it produces very quick results.
A suitable (waterproof) container.
A piece of absorbent cloth / flannel or even some sturdy kitchen paper
Some Cress seeds
Fold the cloth over on itself a few times so that it is quite thick and then cut it to a size that fits neatly into the container.
Moisten the cloth and sprinkle the seeds onto it, forming a thick but single layer, so that all seeds are in contact with the moist cloth.
Place the container in a warm dark place, for instance the bottom of your airing-cupboard, and leave it there until the seeds begin to sprout - checking at least twice a day to see when this occurs. Germination will normally take about 2 days.
When the seeds begin to sprout, move the container to a light location, such as a windowsill, and let them grow. Check the moistness of the cloth frequently, and add a little more water as necessary. In a few days you should get something like this:
You know what to do now - cut the Cress with scissors and use it as a salad ingredient!