This is one of my best ways to beat cabin fever in the winter: join a fall and winter tennis league.
The indoor courts are heated in the winter, air-conditioned in the summer and are very well lit. They have also have/offer tennis instruction, outdoor american green clay courts, pro shop, gym, aerobics classes, racquetball and a bar area in the lobby (how cool is that!).
The staff and fellow members here are friendly, down-to-earth and cool overall.