*Round Hill Hall, a 19th century bed and breakfast house, will have its first Halloween Haunted House tonight from 6 to 9 p.m. The house is open to children and adults, with an adult Halloween Party following the scare. "The Monster Mash" party will begin at 8 p.m. and feature live music by Oasis. Innkeepers Gloriana May and Mary Lou will serve a special Halloween brew. Tickets are $2 per child for the Haunted House and $3 per adult for the house and party. Costumed guests are welcome and prizes will be awarded in several costume categories. All proceeds will go to the Round Hill Volunteer Fire Department and Rescue Squad. The Hall is 13 miles west of Leesburg, in the Old Dr. Khulman House. For further information and adult reservations for the "Monster Mash," or a Nov. 8 "Fifties Day" at the Hall, call 703-338-9221.

*The Dale City Arts and Crafts Club will hold its 17th Annual Crafts Bazaar from 9 a.m. to 3 p.m. Nov. 2 at the Hillendale Fire Station on Dale Boulevard, Dale City. Dubbed "Homespun Holidays," the bazaar will offer sweets, needlework, Christmas gifts and potpourri for sale. There will also be a Secret Shop for children under 12 to do their Christmas shopping without parents. And don't overlook the raffle of a cord of firewood, as well as various special holiday gifts and decorations. Cash and checks will be accepted for payment. For further information, call 590-4213 or 670-8009.

*The Tournament of Bands will sponsor a marching band show at 4 p.m. Nov. 2 at the Mount Vernon High School stadium. High school marching bands from the Washington area, central and southern Virginia will participate. Admission is $3 for adults and $2 for children. For more information, call John Muzzi at 703-631-9887 or David Priester at 703-670-8167.

*The United Community Ministries is seeking volunteers to drive clients to their medical appointments. Senior citizens are in need of the individualized service provided by volunteers. If you can offer your services at least once a month, call Addy Krizek at 768-7106.

The ministries is a nonprofit agency that provides emergency assistance to the needy along the Rte. 1 corridor south of Alexandria.

*"In the Second Place," Mount Olivet Preschool's annual sale of recycled children's clothing, books, toys and equipment, will be held from 10 a.m. to 2 p.m. Nov. 2 at 1500 N. Glebe Rd. in Arlington. Free admission. For further information, call Mount Olivet Preschool at 527-5508. -- Dianne Saenz