Visit the Great Museums: London's state museums and galleries -- including most of the big names -- are free to enter. World-class treasure troves where you can roam without charge include the British Museum, National Gallery, National Portrait Gallery, Tate Britain, Tate Modern, Natural History Museum, Science Museum, Victoria & Albert Museum, Museum of London, and Sir John Soane's Museum. And don't forget the British Library with its collection of literary gems.

Watch the Changing of the Guard: The Buckingham Palace event has more pomp and circumstance than any other royal ceremony on earth, but the two daily changes at Horse Guards, Whitehall, SW1 (tel. 020/7414-2479), the headquarters of the Queen's Household Cavalry Mounted Regiment, is both more accessible and more fun.

Take in Fresh Air and a City View: North of the River, Hampstead Heath, NW3 (tel. 020/7482-7073), offers miles of woodland trails and the best vistas over low-rise suburbia to the architectural icons of the center. To the south, the heights of Greenwich Park, SE10 (tel. 020/8858-2608), enjoy a panoramic sweep that takes in the royal borough's 18th-century maritime architecture and the steel-and-glass edifices of Canary Wharf. Recent cold winters have even seen the hill used by local snowboarders.

Dine on the Cheap: Away from the main tourist drag and the Michelin-starred hotspots, London is surprisingly well equipped with affordable, tasty places to enjoy a full meal for under £15. Among the best are the fiery Szechuan flavors of Gourmet San, 261 Bethnal Green Rd., E2 (tel. 020/7729-8388), and the West End's venerable budget pitstop, the Stockpot, 38 Panton St., SW1 (tel. 020/7839-5142; www.stockpotlondon.co.uk).

Go to the Library: The best and most easily accessible of London's specialist (and free) libraries is the Wellcome Collection, 183 Euston Rd., NW1 (tel. 020/7611-8722; www.wellcomecollection.org), which houses a grisly cornucopia of medical materials, including books, paintings, and drawings. Staff offer free tours and workshops to help guide you through the intricacies of a unique collection.

Shop for Vintage Threads: The East End Thrift Store, Assembly Passage, E1 (tel. 020/7423-9700), has a warehouse full of vintage clothes for men and women, all at good prices if you hunt hard.

Catch a Free Event in the Center of the City: From the Lord Mayor's Show to the Notting Hill Carnival, almost every major public event in the capital costs nothing to attend. Call in at the Britain & London Visitor Centre, 1 Lower Regent St., SW1 (tel. 08701/566-366; www.visitlondon.com), and inquire about what's on while you're here.