if you like Risk, you should check out
Conquer Club
One of the best risk sites online, tons of different maps and game modes, tournaments and the like.
I was really active on there a while back but haven't played in a year or so.
back to topic - another good casual party game is a dice game which goes by many names: 10000, farkle, zilch and probably others.
the goal is to reach a score of 10k, any number of players is fine.
you roll 7 dice. you score 100 points for each 1, 50 points for each 5, nothing else scores unless you roll a three of a kind. if you roll 3 of any number you can take them as a set for 100 x die number (example, three 3s = 300) while a set of three 1s = 1000.
on each roll, you have to have at least 1 scoring die or your turn is over and you lose any points for dice that you had set aside that turn. you can set any number of scoring dice aside to count towards your score and continue rolling the remaining dice. If you manage to set aside all 7 dice, you can reroll all of them to continue going.
you have to set aside at least 1 scoring die to reroll the rest. after setting aside a scoring die, you can choose to stop rolling to add the dice that have been set aside to your score and end your turn.
you have to roll 1000 or more in a turn to 'get on the board' meaning until you have set aside at least 1000 points you cant choose to stop rolling and take whatever points you have. (you can't stop at 800 if you are not on the board) however, once you have gotten on the board, you can stop at any scoring value.
another favorite of ours is "
To Court the King" which is kind of like yahtzee but where you can pick up cards that give you special abilities to modify your rolls in various ways.
