The key is to find a girl who is a sports fan but doesn't really hold any allegiances. When I started dating the girl I'm currently with, she liked college football and watching the NHL and NFL, but wasn't a fan of any team persay, other than UMD football.
Well, a Caps game, Steelers training camp, and a Nats game later, she's now a Caps-Steelers-Nats fan. Best part is, she watches the Nats every night and will give me updates if I'm busy.
I hear that. My wife endured my conversion from Yankee to Nats fan and jumped right on board with me since she had no particular allegiances anyway. The closest thing to a "fan" she came to was the Saints since she grew up in Southern Mississippi and there were no baseball teams to follow (that's why I'm a sorta Saints fan - I married into it). Now my wife is a Nats and Caps fan to go along with her Saints.
On a side note: I'LL BE WATCHING TONIGHT!!!