There is not much difference between a Constellation and an Asterism. It is just that the constellation has made it to the official list of eighty eight, areas of sky as defined by the IAU.
There are plenty of asterisms that exist in the sky and lore, large such as the Big Dipper & small such as the Kemble's Cascade and the Coathangar. Asterisms may be seasonal like the Summer triangle, The Winter Hexagon, The Square of Pegasus in Autumn and the Diamond of Virgo in Spring. An asterism may span several constallations e.g. Summer Triangle or it may be one single constellation e.g. the "W" or the Cassiopeia.
Here are three asterisms which I photographed this morning. The Pleiades, Hyades and the Kids of Auriga. The area of this part of the sky is rich in bright stars and star clusters. The area is presently also being populated by the King of Planets - Jupiter as well as the only Dwarf Planet in the inner part of the Solar System - Ceres. (See the photo below for annotations).
The details of the astrophoto are as follows:
Camera: Canon 5D Mark II
Lens: Rockinon 35mm prime lens
Exposure: 90 seconds
No. of Exposures: 8 exposures (stacked)
Mount: Polarie mount (tracking the stars)
Date: 24 September 2012
Time: during the astronomical twilight