Seriously. The internet is just amazing.
Favourite example so far:
"Prior to the GVS, which took place over around 200 years, Chaucer rhymed food, good and blood (sounding similar to goad). With Shakespeare, after the GVS, the three words still rhymed, although by that time all of them rhymed with food. More recently, good and blood have independently shifted their pronunciations again."
(Richard Watson Todd, Much Ado About English: Up and Down the Bizarre Byways of a Fascinating Language. Nicholas Brealey, 2006)from