St. John's College outfits its Annapolis campus for weddings, and the University of Maryland College Park opens its armory for national jump-rope competitions. St. Mary's College lets CIA agents wander amid serenity of its river-edged lawns, and Hood College gives local teen-gers lessons in how to play rock in their garage.

Those are just some of the surprises to be found on college campuses this summer.

Weekend or weeklong respites for academics, alumni, children, taxidermists, bowling alley managers, cyclists and bird watchers alike have become a major source of good will and extra cash for higher education nationwide.

Though not willing to play hotel operators to just any tourists, many Maryland colleges say their dorms, their dining halls and their swimming pools are increasingly filled to capacity in the off-season by non-profit or education-related groups.

"There's really a different rhythm in the summer," says Chris Cihlar of St. Mary's College, which has hosted cyclists and sailors by the thousands. Four times as many people pass through campus in summer than during the academic year, she says, including 5,000 to 7,000 for the annual Governor's Cup Yacht Race. "Where else could you find enough showers and bathrooms?"

Squeezed in around summer school sessions on big campuses like College Park or filling otherwise empty space at Goucher and Notre Dame, the campus conference-and-event industry has climbed dramatically in the past decade as outsiders search for solitude, beauty and low cost and colleges look for new sources of revenue.

A decade ago, groups looking for a relatively cheap source of housing had to wind their own way through the bureaucracy. Today, many campuses have set up offices to handle the package deals groups require -- lodging, meeting space, shuttle service, and catering.

"We're the best deal in town," says Jeanette Hoffman, wharranges accommodations for rentals business groups, wedding parties and lawmakers at St. John's College. "We do it mostly for public relations, not for the money," she says.

Colleges account for 8 percent of the nationwide meeting business, according to Meeting News, an industry trade journal. More than 600 U.S., Canadian and Australian colleges now belong to a professional association for college conference directors, up from 11 when the Colorado-based group was founded in 1981, according to James M. Limbaugh, Frostburg State University administrator and a director of the professional group.

"They come for ambience as much as cost," he said.

For college communities, the benefits can be enormous: jobs for students and for food service workers, janitors and faculty otherwise laid off in summer, extra income to spend on academics during the year, and a chance to show off the campus to potential students -- or relatives of potential students.

"For every couple that comes to a marriage encounter, there could be an 18-year-old at home," said Sally Allison, head of conferences at Towson State University, which expects 1,200 people for a regional marriage counseling weekend affiliated with the Catholic Church in August. "It's a real recruiting tool," she said.

The catch is that overnight guests sometimes must bring their own linens and almost always put up with group showers.

But they don't seem to mind.

For years colleges have opened their doors to the outside community in summer, offering everything from the use of the swimming pool to summer concerts, courses, lectures and athletic camps for kids.

What happens on college campuses in the summer nowadays is part good will, part academic necessity and part happenstance -- such as when a popular program grows too big to handle other times of year.

Such is the case with the National Orchestral Institute, a three-week camp at College Park for aspiring musicians, taught by top conductors and first-chair musicians from orchestras around the country. It culminates in the International Piano Competition. The 10-year-old event is one of the premier competitions in music and draws 400 volunteers from the campus neighborhood to help raise money and host events.

College Park is the busiest state campus in summer, bringing in more than $1.2 million in gross revenues. In past years, said Melvin Bernstein, dean of summer programs at College Park, profits have been used to computerize the campus and purchase academic equipment.

He runs a giant summer school program, which generates 72,000 academic credit hours, or nearly half the wintertime enrollment. More than 15,000 students in 68 disciplines study in summer.

Public campuses began to be used heavily in summer after World War II to accommodate the academic needs of returning veterans. At College Park and many other campuses, conference services evolved in response to demands from faculty who needed a place to host colleagues and academic exchanges at all times of year.

Even today, says Susan Warren, assistant director of the five-year-old conference office at College Park, most summer conference business is generated from the campus itself. Last year, the campus's institute of microbiology hosted 2,000 scientists from around the world for an international congress of systematic and evolutionary biology. This year, the campus' institute for philosophy and public policy will host a group of philosophers studying the changing roles of the American judge.

"Business is growing. We've seen more and more universities holding educationally-oriented kinds of programs," she said.

Now at College Park, some academics are eyeing the summer months as the time to give students things they can't get during the year. Such is the case with a new, intensive six-week residential program in Japanese language and culture for engineering students.

The first of its kind in the Washington-area and one of the few on the East Coast, the summer study program was set up to help solve a national dilemma -- the scarcity of U.S. engineers who can understand and translate the volumes of Japanese treatises in their subject. Language study isn't possible during the year because the engineering curriculum allows little time for anything but engineering.

The new program, run jointly by the College of Arts and Humanities and the College of Engineering, is also being marketed to Washington professionals.

What made it possible is a language house on the College Park campus that opened for students last year. It is equipped with apartments, a cafe, and computers that operate only in foreign languages. Residents converse in the language they study.

The language house will also be used this summer to teach Chinese to high school teachers from around the country in the largest such program funded by the National Endowment for the Humanities.

At public colleges and universities, revenues from summer room rentals and catering reduces the cost of room and board to students during the academic year. Unlike academic buildings or equipment that are paid for by taxpayers, dorms, dining halls, parking lots, athletic facilities and other non-academic facilities are paid for entirely from student fees. Using these facilities during the summer keeps costs lower during the year, officials say.

For private colleges, which depend on student tuition and private giving to operate during the year, summer guest services are an increasingly critical source of revenue.

Summertime studies by nuns in the 1930s and 1940s helped then all-male Mount St. Mary's meet the monthly payroll during the school year. Today, profits of up to $300,000 from summer guests pay employee pension and salary costs. The alternative, college officials say, is higher tuition.

In Maryland, the biggest users of college campuses after students and faculty are state and federal governments, religious groups and Elderhostel Inc., the Boston-based, non-profit group that arranges year-round educational programs for senior citizens at colleges around the world.

In a few cases, private companies that want an alternative to fancy resorts to train employees are being allowed on campus.

"They're looking for the academic atmosphere, not the party," said George Gelles, who is in charge of conferences at Mount St. Mary's College in Emmitsburg.

Non-profit, tax-exempt education institutions say they are careful avoid competition with private businesses, and for the most part they try to stick with academic-related business.

Conference services were welcomed by Westminster, where Western Maryland College opened a Quality Inn on land it owned near campus in partnership with a private developer. Other hotel chains followed, taking the overflow.