A best before date indicates when a food is at its best. It can still be eaten after this date, there just might be a reduction in quality. However, in most cases this is something that is barely noticeable. Over time the texture and flavour of the food might change, but in most cases it will still be edible.
There are several websites that sell food which is just past its best before date. This is often for a lower price than the RRP. A list of these sites can be found below.
Haggl 