Product review (5 stars): THE Dryer Belt
Consult model and part number first, but if this is the belt for your dryer keep an extra one handy.  If you're at all good with tools, the installation is simple.  When the old belt snaps you can install this one and have the dryer going again in under 30 minutes, instead of having to haul the damp clothes to a laundramat or a friend's house.