Our group plays more card games than boardgames... they're more easily portable from house to house as well.
Our favorites are:
Graverobbers from Outer Space
This one is great if you like those old cheesy horror movies (or even those new cheesy horror movies). Each player builds their own movies with characters (like the High School Vice Principal or the Annoying Little Brother), locations (like the Cabin in the Woods or the Funhouse) and props (like the Chainsaw or the First Aid Kit), and attacks their opponent's movies with monsters (like Dracula or Carnivorous Slugs). There are also special effects cards, which are used like instants in Magic and can be played by anyone at any time.
Munchkin
Someone else mentioned this one, and I wanted to second that. It's all about killing monsters and taking their stuff, and keeping your buddies from doing the same, but it's all in good fun... with monsters like the Wight Brothers and the Gelatinous Octohedron and treasure like Kneepads of Allure and the Boots of Butt-kicking how can you go wrong?
Fantasy Business
You're a medieval shop owner striving for market share from the local adventurers. Corner the market on Swords and Spell Scrolls and demand outrageous prices or undercut your opponents prices to steal his busniess from him. One of my favorite parts of this game was playing with the sack of coins it comes with.
Wizard
This is kind of like spades without partners and with a variable trump suit. Wizards and Jesters add another level, with Wizards being the super trump, and Jesters the lowest of the low.
Royalty
It's a cross between scrabble and rummy, plus you can steal your opponents words to make new words of your own.
Just remembered one more that I bought and enjoyed on recommendation from these boards:
Once Upon a Time
The players use the fairy tale elements on the cards they draw (like witches, cottages in the forest, and talking animals for example) to tell a story, with the goal of leading it up to their Happy Ending card. Other players can interrupt however and take over the story to lead it to their own happy ending.
Hope these help.
