Old maid (with ruth stout as the maid), Crazy Eights, War, Go Fish, etc are all great for playing with kids. Poker (5 card draw, 5 card stud, blackjack, etc) are nice for fun times. Solitaire is always nice if you can't find a friend. Hearts, Spades, and other trick taking games are good for 4 players. Check your local library for books on card games and I bet you'll find a lot of material to try.
The Crazy Permies game is one my wife and I came up with. It's an association game. You deal 7 cards to each player and then lay the rest of the cards face down in a pile (stack) in front of you. Flip over the first card and begin the game. I've copy/pasted the post on this I made on Facebook when we were still developing the game:
My wife and I are working on a game based on association. The idea is to pass out 7 cards to each player, place the deck in the middle, and show the top card face up next to the deck. The person to the right of the dealer starts and has to play a card that relates to the permaculture value of the card. For example, if the card that is face up is Wind & Berms (5 of Diamonds) then the player might play Hugelkultur (Ace of Clubs) because it is often built into a smaller berm style system. These types of associations need to be explained as you lay the card down. Saying "because it's also part of permaculture" is not allowed... one must try to be detailed in why the two associate. If the player does not have a card they can associate, they may opt to play the traditional "match face or suit" but they must still draw after playing if they go this route. If they can't even match face or suit, they must draw and play no card, passing to the next player in turn. The person who plays the last card in their hand wins.
Egyptian Rat Screw (a variant of slapjack)
Spoons (a fun multiplayer sneaky game)
how to play wrote: Object of the game is to get a spoon or else your out. Start with one less spoon then number of players. Everyone get four cards, then start passing the cards around until someone matches four cards and when you see a spoon being picked up, get one or your out. Keep going until you have a winner!! Have fun!!! Trick- don't just look at your cards - watch the spoons.