Time for players to start thinking about playing basketball this March, spring and summer in AAU, MBR, MAC, etc Games and Tournaments. Organize a team, try out for a team, just make sure to find a team to play on.
Time to work on your weakness during the off season. Ask your coach what he/her thinks what you need to work on during the off season.
Time to get into the weight room for you older players. Start a new strength/quickness program or update your old one.
Spend some time when the weather gets better to shoot and work in your backyard hoop or the nearest outdoor court to your home.