Children and young adults ages 8 to 23 may register today and Friday for a Nov. 7 to 8 baseball clinic being offered in Prince William County by the Doyle Baseball School of Winter Haven, Fla. The clinic, sponsored by the Prince William County Park Authority and featuring big league players and coaches, will begin at 10 a.m. both days and wind up at 4. There is a $50 registration fee for the two-day session, being held at the county stadium on Davis Ford Road. For more information or to register, contact Sharon Hartman at 703-361-7181.

"Jungle Book" will be performed by the Kinney and Company Youth Theatre at 7 p.m. tomorrow and at 11 a.m. Saturday at the Lee Center in Alexandria. "Jungle Book," based on Rudyard Kipling's works, is a musical play that follows the adventures of Mowgli, a boy raised by wolves in India who, at age 10, returns to his village. The cast is composed of 25 children and four members of the Alexandria Harmonizers. Kinney and Company is a nonprofit theater formed in 1985 for children and young adults.

Tickets -- $4 for adults and $2 for children -- are available at the door or in advance by calling 684-KIDS. Lee Center is at 1108 Jefferson St.

Dare to discover what creatures loiter in the woods on Halloween night by signing up now to attend "Haunts of Nature," a haunted hike through Potomac Overlook Regional Park. Starting at 7 p.m. Saturday at the Potomac Overlook Nature Center, children and their families will be escorted through the woods by a guide in costume to experience the haunts of Halloween. Participants are encouraged to come in costume. Refreshments will be served after the event.

The walk is free, but reservations are required. Potomac Overlook Regional Park is in north Arlington, at the end of Marcey Road, off Military Road. Call 528-5406 for information.

Treat your child to tricks and games at a Halloween Fun Fair from 10 a.m. to 2 p.m. Saturday at Bailey's Elementary School in Falls Church. Two spooky houses, a raffle, children's games, international food, a moon walk and pony rides will entertain fair-goers, and a fortuneteller and magician will be on hand. Admission is free. The fair is sponsored by Bailey's Elementary School PTA. The school is at 6111 Knollwood Dr. For more information, call 578-3140.

Sport your Halloween best at the Fifth Annual Phantom Ballroom Costume Dance from 8 p.m. to 1 a.m. Saturday and benefit a scholarship and grant program for the Alexandria Commission on Disabled Persons. Live entertainment by The Uptown Rhythm Kings and refreshments will be provided. Parking should be ample for the dance, which will take place at the VVKR building, 901 North Pitt St., Alexandria. Tickets cost $10 and may be bought at the door or in advance at Backyard Boats Showroom on Franklin and Union streets, or the Hard Times Cafe, 1404 King St. For more information, call 838-0711 or 548-1375.

Secondhand books for bargain prices will be available at the Fall Book Sale Saturday and Sunday at the Arlington Central Library. Sponsored by the Friends of the Arlington County Library, the sale will take place from 9 a.m. to 4:30 p.m. on Saturday and 1 to 5 p.m. on Sunday. The library is at 1015 North Quincy St. For more information, call 284-8181.