While in college, I once gathered entries from Dictionary of Changes in Meaning by Adrian Room, a book that gives obsolete definitions of common English words and traces their evolution to their current meanings. In this diary I give a sampling of what I collected.
I had access to books like that at my university's library. If you don't wish to buy such a book but are looking for a free, online source for looking up word etymologies, go here. If you have any more examples of words that have changed in meaning (whether over the last few decades or the last couple of thousand years), feel free to provide them in the comments.
And if you have absolutely no interest in this topic whatsoever, what are you doing up at this hour?
algebra: bone-setting
buxom: obedient
coffin: basket
computer: person who does computations
corpse: a living person's body
friend: lover
garbage: animal food
girl: child of either sex
grammar: the study of Latin
hussy: housewife
jargon: twittering of birds
jest: noble deed
kill: to strike or beat
knight: boy, youth
lair: bed
larva: ghost
lewd: not a member of the clergy
litter: portable couch
nice: foolish
nosy: having a large nose
passenger: traveler on foot
poison: any liquid mixture, not necessarily toxic
sagacious: having a keen sense of smell
silly: blessed
snob: shoemaker
toilet: cloth wrapping
tomboy: boisterous boy