When I was a kid I got and filled up a couple of coin collecting books - one for pennies, one for dimes, and one for nickels. I think I actually completed the book except for a couple of the really hard-to-find dimes.
I seem to accumulate a lot of change over time (mostly because of my murse - it builds up), and every once in a while I pull out a handful and look at them.
The pennies particularly strike me. The newer ones have the shield back rather than the Lincoln Memorial. The ones before 1983(ish) were of the old metal blend before they changed over to the cheaper, shinier mix. (HINT: If you ever get a pressed penny at an attraction or amusement park, make sure to use one of those older, duller pennies - the impression is drastically better.) Every once in a while I hit one of those "ONE CENT" reverses (I keep those). And the dates! Just now I ran across a penny from 1941. That's almost as old as my mother, yet it's in good condition (for a circulated coin) - you can read the date and the details clearly. Where this coin must have gone over the years! I can only imagine.
I also check out the quarters. For a while I was collecting the state quarters, but have no idea where my collection is on that. I also keep a look out for the 1976 bicentennial quarters, which were a big deal at the time (this was all before they started mixing up coinage and bills in the 90's and 00's to keep things interesting). I keep those, too.
I also really love the dollar coins. I always try to remember to get a whole bunch before Pennsic because they're fun to toss into the buskers' bowls along the road to the food court - you're giving them something substantial, and it looks pretty sitting there in the sunlight. (Besides, no one had bills in the Medieval period.) I definitely like the presidential series, but I admire the Sacagawea coins, too. I wasn't as hip on the Susan B.'s, only because they were also silver. (Canadian twoonies are neat - a gold center in a silver ring! Those are pretty.) Before that, my friend Carson used to live in NYC and he'd go to the depository and get a sack full of the Eisenhower dollars - those were HUGE, and he loved using them at Pennsic.
Sometimes I'll run across a JFK half dollar, which I'll also keep. My mother has a few liberty head dimes and really old nickels, too.
Anyway, was just musing. Carry on. :)