The Washington Monument has a new timed entry system. Through Sept. 2, free tickets timed for half-hour intervals are available on the day of admission on a first-come, first-served basis from the nearby 15th Street Ticket Kiosk. The new system was designed to reduce visitor waiting time, which can be as long as three hours. Tickets can also be ordered through Ticketmaster ( 505-5040) at $1.50 a ticket, plus 50 cents handling per order. No tickets are required after 8 p.m. during summer hours, which began last month. Information: (301) 350-8830.