In late November, after Chapel Hill empties of its homeward-bound college students, Franklin Street can seem almost as desolate as downtown Durham. Yet for a number of Triangle residents the coziest place to spend Thanksgiving is a little underground watering hole off the main drag. For 19 years, the Cave has hosted a Thanksgiving Day Potluck and Celebrity Jam, a late afternoon stuff-yourself-and-sit-back affair. Folks bring their favorite Thanksgiving dishes and their musical instruments, and the Cave supplies a couple of turkeys, a ham and that comfortably dim lighting that takes years off your face. This event is a longtime tradition with locals; kids are welcome, as are newcomers. For more information, call 968-9308.