I grew up playing games with the whole family, and constant cards games with my siblings or solitaire when I couldn't get any of them to participate. I used to know over a dozen different kinds of Solitaire; nowadays I only play the two simplest versions, probably because they're the speediest, which gives instant satisfaction and keeps you playing.
My mom's family was full of card sharks, and we learned how to play Gin rummy and Crazy Eights and Hearts and I Doubt It (which I learned later in college was actually called Bullshit). Both my parents and all my relatives played Bridge. My dad tried to teach us Pinochle when we were pretty young; it didn't end well, but I took to Euchre during my working summers at Michigan State like a champ. We learned how to shuffle like pros, snapping the cards together down and riffling the bridge up.
There were always decks of cards laying about, ready for use and willing partners. Nowadays, the only time I ever play cards is when I'm at my mom's or with my sister...it's automatic: we both go for a deck.
When I was pregnant with Martin, my mom came to stay around the time the baby was due, and she and I waited out the long three weeks he spent NOT being born already, playing cards. She taught me how to play Cribbage, which I had somehow never managed to get the hang of...probably because there is a lot of math, albeit simple counting, involved. The game has been around for over 400 years, and it's easy to see why: it's fast, fun and very addictive.
If you don't know the rules of Cribbage, you can get up to speed here, but basically, you count points of pairs, cards that add up to 15, and runs in hands of 4 cards, until your peg reaches the end of the cribbage board. It's really fun, and it's good for me and my math-retarded brain.
In a 2-player game of Cribbage, each player is dealt 6 cards and must discard 2 into the "crib" which belongs to the dealer. So when you are the dealer, you want to put 2 cards from your hand into the crib that will give you the possibility of points. If you are not the dealer, you want to put 2 cards into the crib that will NOT give the dealer any points. The dealer counts the points of the crib after counting their hand and adds them to their total score each turn.
We play a LOT of Cribbage at my mom's. When we get up, after breakfast, before and during lunch, in the afternoon, in the evening, before bed. Mostly it's my sister and I playing, sometimes my mom, and sometimes one or more of the kids who learned how to play last time we were all together, but haven't played often enough to remember much about it between times. They think it's funny to watch Sarah and I play as well, because we are very competitive and steal the deal and points from each other whenever we have a chance, plus we both gloat when we win and sulk when we lose. We're very vocal about both our excellent hands and our crap ones.
At some point during our first week at my mom's after vacation, Martin asked if anyone had ever tried to play "Opposite Cribbage". Sarah and I looked at each other and said, "No. How would that even work...wait, let's see..." and we started to play and it was HILARIOUS. The rules are simple: you play Cribbage but any points you would normally earn go to your opponent.
So, when you are the dealer, even though the crib is yours, the points in it go to your opponent, so you want to discard 2 cards that WON'T put points in the crib, and if you are not the dealer, you want to put 2 cards in the crib that WILL give you points. And you want to keep no points in your hand as well, because the points will go to your opponent. Get it? The only point you get from yourself is if you say "Go" (because a Go point usually goes to your opponent and this is opposite rules). If you have been playing Cribbage for a week, switching around this way is brain-damaging, but very, very fun. Martin christened the new game Crappage.
If possible, there was even more vocal ululation and distress and swearing than during normal Cribbage. I highly recommend it if you play cards and know Cribbage. :D