ONCE, NOT so long ago, hotels that were a step ahead of the competition boasted of a television set in every room. Now TV is standard equipment, and there's a new high-tech lure to draw the paying guests. Enter the hotel-room computer.

In recent weeks, Travelhost Inc. of Dallas, the people who publish those city guides travelers find on their bedroom dressers, have begun installing computers in hotel rooms across the country. In June alone, the company expects to supply 5,000 to 6,000 rooms, and by the end of the year the forecast is 100,000 computer-equipped rooms.

When one looks at "the history of hotel amenities," says J. Roger Thrailkill, vice president of marketing for Travelhost, you see hotels quickly adopting "what's in our homes: phones, TV, color TV." With today's apparent popularity of home computers, could a computer in our home-away-from-home be far behind?

At the moment, the devices (utilizing the room's TV screen) are aimed at business travelers, who make up a substantial portion of most hotels' clientele. Orders have come from a wide range of hotels, says Thrailkill, including individual hotels among such chains as Marriott, Sheraton, Quality Inn, Holiday Inn, Hilton, Ramada Inn and Best Western.

So far, the only Washington hotel to install computers is the Anthony House, which placed them in all 97 rooms during the first week in June. "I think it's going to be like TV sets," agrees general manager Gary Stremel, whose hotel caters primarily to business travelers. "They started out as an option. Now every hotel has to have them."

Among the computer's anticipated uses:

* Calling up a copy of the Official Airline Guide, with complete flight times and fares. This should prove handy, says Thrailkill, for business people who have to make last-minute changes of itinerary.

* Making the necessary reservations, through a computer-linked travel agency.

* Receiving messages from the home office. Over the long term, Thrailkill thinks this may be the computer's most important use. First a traveler obtains a system identification number. Using that number, the traveler can call up messages after checking into his or her room. The home office can send the messages at anytime, even if it doesn't know in which hotel the employe is staying.

* Dispatching messages, or even daily sales reports, to the home office. The Travelhost computer is quite compatible with most office systems, says Thrailkill. Generally, the only requirement is that the system have access to one of the public information networks, such as Telenet.

* Obtaining the latest United Press International news and sports along with stock market reports.

The minimum charge anytime the computer is turned on is $3, with the per-minute cost for use ranging from 17 to 34 cents, depending on the time of day. Costs will be billed to a credit card account.

Beyond the business uses, Travelhost also is offering a choice of 50 video games, which could prove tempting to a bored traveler.

But how do you explain an evening of game time on an expense account?

SUMMER TREE HOUSE: Ever wish you could spend a night in a back yard tree house?

Sooner or later, somebody manages to help us grownups realize our childhood dreams. At Maple Tree Camp, a 26-acre campground in Gapland, Md. (west of Frederick), they have built four small, rustic houses perched in the thick foliage of oaks and maples at bird's-nest height.

Three are supplied with wooden bunks and a fourth, called a "tree cottage," has two double beds and a table and benches. All have screens opened to the night breezes.

Scramble up the seven-foot ladder, spread out a sleeping bag and you have fulfilled another dream.

The three smaller tree houses rent for $4 per night per person, with room, respectively, for 4, 6 and 8 campers. The charge for the cottage is $20 a night for up to four people. Reservations are necessary.

A small area, Maple Tree has a total of only l4 campsites, most of them for tents. Each has a grill and table. Water, restrooms and an outdoor shower are centrally located.

The campground is a place for relaxing in a hammock, says manager Dola Burkentine, who points out, "We don't provide any entertainment." Nearby, however, are historic Harpers Ferry and Antietam National Battlefield for sightseeing; the Shenandoah and Potomac rivers for canoeing and rafting; and the Appalachian Trail (which borders Maple Tree) for hiking.

As for that other childhood dream: Yes, they do have an Indian teepee for rent, a canvas replica of a Cherokee lodging. The charge is $4 per person for up to four adults.

At night, by the light of a kerosene lamp, says Burkentine, the atmosphere within the teepee is delightful.

For information: Maple Tree Camp, Ltd., Townsend Road, Gapland, Md. 21736 or (301) 432-5585.

NORTH ATLANTIC Memorial: The Coast Guard cutter Mohawk, credited with the rescue of 293 survivors from an Army transport ship in 1942, has been restored and has just entered new duty as a living museum and a memorial to the Battle of the North Atlantic during World War II.

Docked on the Christina River in Wilmington, Del., less than a mile from where she was launched in 1934, the 165-foot vessel is open to the public for tours every Saturday and Sunday from noon to 5 p.m. through October.

More than 20,000 volunteer man-hours have been invested in refurbishing the Mohawk in the past two years, much of it contributed by veterans of the bitter ocean war. One of the volunteer carpenters was 17 years old when he joined the Mohawk in 1940 as a carpenter's mate.

A year before Pearl Harbor, the Mohawk began service as a convoy escort, shepherding British cargo ships across the North Atlantic, continuing the escort assignment until the end of the war. From 1942 to 1945, she launched 14 attacks against enemy submarines, escaping damage herself.

After the war, the Mohawk (renamed the Philadelphia) served as a pilot station in the Delaware Bay shipping channels. In 1981, Mohawk Inc., a non-profit corporation formed to renovate the cutter, purchased her for $1 and restored the original name.

The cutter is still operational, and there are tentative plans to take it on a cruise to Philadelphia and Baltimore harbors. A tour includes visits to the bridge, the crew's quarters, the engine room and state rooms. There also are displays of the ship's history.

For more information: Mohawk Inc., 901 Washington St., Wilmington, Del. 19801 or (302) 656-0400.

NEW YORK FARES: It's a little bit cheaper now to get to Manhattan.

Trailways recently dropped it's one-way Washington-to-New York bus fare by $5, and Greyhound shortly followed, bringing the new fare for the four-hour and 20-minute trip to $20.

As a comparison, Amtrak currently is charging $37 one way, $56 round trip; the Metroliner is $46 one way; People Express airline (to Newark) is $35 one way weekdays until 7 p.m. and $23 weekends and evenings from 7; Eastern Airlines' shuttle (to La Guardia) is $65 one way on weekdays and Sunday afternoons and $29 all-day Saturday and until noon Sunday; New York Air's La Guardia shuttle is $65 weekdays and Sunday evenings. From Saturday morning to Sundays at 3:30 p.m. some seats are $29 and the rest are $45.

WESTERN UPDATE: How have the winter storms and rapid spring runoffs affected travel in California and Utah, two states particularly hard hit?

In the scenic Big Sur area of California, large mudslides and washouts continue to block the popular coastal drive between San Francisco and Los Angeles along State Route 1. This section of the twisting two-lane road is not expected to be open to through traffic until the first part of August.

North of San Francisco, a major washout has reduced the coastal route to one lane at Fort Ross, south of Mendocino, hampering traffic flow along this equally scenic and popular drive. The roadway in this section, which remains open, is not expected to be fully restored until the end of the summer.

In Utah, travel officials are worried that tourists may be frightened away from the state by reports of the recent flooding in Salt Lake City. So they are issuing an advisory pointing out that the southern portion of the state hss been relatively unaffected, and this is where the five national parks that are among Utah's major attractions are located. One exception are some whitewater rafting trips down portions of the Colorado River above the Glen Canyon Dam, which have been temporarily discontinued because of "treacherous" water.