Anyone who is still in Washington at the end of August is by now soppy with self-pity. It seems that everyone else is off somewhere, lapping up the sea breezes, fishing, sailing, touring. The fact that the streets are still crowded with people is inexplicable: You know in your heart that simply no one is left in the city.

Poor you. You deserve a treat, an extravaganza to provide you with the month's most memorable lunch hour or evening. If, when you sit down and think about it, you realize that not quite everyone has left, you might get together a group of friends and split the costs of one of the following movable feasts.

For $60 an hour you can have a Rolls-Royce pick you up at your office and drive you and a companion around during lunch hour. Wear turbans and have the driver cruise the Washington Monument while the tourists stare. You may feel that you're a schlump to be in Washington in August; they'll think you're a sheik.

Since you're using up your lunch hour, you will want to eat. A chilled bottle of champagne will take care of summer's thirst, and Sutton Place Gourmet (3201 New Mexico Ave. NW, 363-5800) can provide the appropriate nibbles for a caviar tasting: Decide which is best, California golden (3 1/2 ounces for $9.99 or 7 ounces, $19.99), Iranian Beluga ($19 an ounce) or Russian red salmon caviar ($4 an ounce).

Serve it on a silver tray edged with plates of toast points, thinly sliced pumpernickel and little dishes of lemon wedges, chopped eggs, onion and parsley.

Have a passer-by take your picture as you emerge from the Rolls and then, when friends return from their far-flung holidays and pull out their vacation photographs, you produce yours. Executive Transportation Services (467-6355) will supply the Rolls. They prefer advance notice, although occasionally on a weekday they can send a car right over.

Have some friends gone to Williamsburg or sent you a postcard from Sturbridge Village? You can explore history on your own in a restored antique car.

Share a rumble seat with a close friend while a chauffeur, costumed in the same period as the car, drives you around. Fill up a hip flask with whiskey (bootleg, of course) and experience the roaring '20s instead of the roaring heat. Brooks Brothers (1840 L St. NW) has pewter hip flasks for $40 and the cars come from Vintage Vehicles (840-0998). They charge $50 an hour with a three-hour minimum. The clock starts running when the car leaves the garage in Gaithersburg. Advance notice and a $75 deposit is required.

If you can't go to London, you can at least climb aboard a London double-decker and tootle around Washington. The Spirit of '76 (529-2575) rents the bus, which seats 70 and costs $44.50 an hour with a 4-hour minimum.

And if you want to turn the ride into a London lunch, pick up lots of fish and chips ($2.69 an order) at Arthur Treacher's, 14th and K streets NW or 1518 Connecticut Ave. NW.

If you prefer the Rhine to the Thames, the Spirit of '76 also leases a Neoplan, a German double-decker with a bar upstairs and downstairs, air conditioning and a bathroom on board. The bus seats 73 people and the base rate is $75 an hour, with extra cost for bartenders or a stocked bar.

You could pretend you were on your way to a German beer garden, picking up platters of food at the German Deli (1331 H St. NW, 347-5732), stocking a variety of German beers and hiring a tuba player to go oompa-ooompa while you whisk around the city. (Look under Musicians in the Yellow Pages, or call the music departments of local universities. If that doesn't turn up a tuba player, there are always tapes.)

If your feelings are hurt because you haven't been invited to The Ranch this August, make it up to yourself by getting back in the saddle again. You can book a lunchtime trail ride through the Rock Creek Park Horse Center (Military and Glover roads NW, 362-0117) for $8.50 an hour. Or, if you're a more experienced rider, $15 will get you a more sophisticated trip.

The rides take place on a first-come basis at 1:30 p.m., 3 p.m., 4:15 p.m. and 5:30 p.m. Tuesday through Sunday with an additional noon ride on Saturday and Sunday. The stable is closed Monday, unless it's a holiday, in which case weekend hours prevail. Groups can prepay to be sure of hitting the trail.

And afterward, it's time to pull out your camping equipment, make a fire, brew coffee (grounds in the boiling water) and share a can of beans with a friend. A chorus or two of the "Streets of Laredo" and then it's back to the city and city slickers.

Heat rises and, when you can no longer bear to be on the streets of Washington, so can you. Chesapeake Balloon Service, Inc., (301-667-6789) offers a champagne charter flight on a hot air balloon: $250 for two.

Although they suggest you allow up to 3 1/2 hours for the excursion, only one hour is actually spent in the air. The rest of the time is taken up with getting from the point of rendezvous to the launch site and then back again from wherever the balloon sets down. Not to mention the time it takes to get your beautiful balloon in the air. Safe ballooning depends on the weather and flights may be canceled if conditions are unfavorable.

Jeff Horrocks of Chesapeake Balloon says that good weather is calm weather, and the best ballooning hours are around dawn or dusk. Give them two to three weeks advance notice and a $100 booking deposit, and you can float right out of August.