We get together every two weeks to game. (At least one of the other players in our group is in a game on the other weekend.) This is a bit of a problem as if we hit something like the 4th of July weekend, we don't push our game session off by a week. We have a four week gap between game sessions. This is to not inconvenience the players that are in a different fortnightly game group, but it annoys us because we have to wait a month. So this is what we're doing.
Fortnightly, we're going to play our normal game. On the off-weeks, when one or more players are in a different game group, we'll get together and do a one-off game. (GMed by whomever wants to bring something to the table.) If we like the game, we'll keep running with it.
I just mentioned this to two of the players in the group and they're pretty excited about it. In fact, I'm a bit more excited about it than I am the regular Shadowrun game. Already, I'm thinking of the one shots and short runs I'd like to try out. Donjon, Primetime Adventures, Crimson Skies (Wushu or Nameless RPG?), that apocalyptic game I've been kicking around, and vs. Pirates.
Yeah, this'll be cool.