Free office space. Just bring energy.

Laid off from other jobs, they needed a base, an office with telephone and Internet service, where they could build a new future. Martini had plenty of space; it was forced by the recession to lay off more than 40 employees, about half its staff, earlier this year. “After the layoff, the energy - the buzz - was gone in the office,’’ recalled company president William Aalerud. “I really missed it. That’s what brings me into work every day.’’

The company sent an e-mail to members of the Boston Society of Architects, offering laid-off professionals space for “nada. Nothing. Free. The big doughnut.’’ More than 40 architects and designers responded, and 13 are now using the space rent-free. They pay only a $50 monthly fee to cover Internet, telephone, and electrical service.

It’s an idea born of necessity as well as the moment. As companies cut jobs in the wake of the recession, the space they own or lease can seem empty or even desolate, a constant reminder of hard times.

Bringing in outside professionals helps restore vitality and bustle in the workplace, and may be a way for the company to do a good deed after executing a difficult decision. And for any worker who is looking for the next big thing, a free office is an affordable resource, a place to go and get on with the job of finding a job.

Architect Jeffrey Mulliken, who was laid off from another company when it downsized earlier this year, moved into his olive-colored office at A.J. Martini on July 1; on the wall, a crisply printed sign announces, “A Crisis is a Terrible Thing to Waste.’’

Mulliken, a workplace strategy specialist who hopes to get some work consulting for companies that are downsizing, has a special appreciation for the arrangement. “Some of the best ideas come out of these kinds of situations,’’ he said.

That’s the hope of Dave Balter, chief executive and founder of BzzAgent, a marketing firm in Boston’s South End that specializes in word-of-mouth campaigns. After the company laid off 12 workers in November, it declined an offer to sublet the space to another firm. Instead, Balter told employees to spread the word that the company was going to make the space available free of charge.

“When we had the layoff, what I saw on people’s faces was not just, ‘What am I going to do?’ but ‘Where am I going to go?’ ’’ said Balter. “I thought we could help people out with that second question.’’

BzzAgent received more than 100 responses to its initial invitation, and offered free desks to 14 local entrepreneurs and designers. As with other companies making similar offers, the people it brought in were not its own former workers, but outsiders who could not afford to rent the space.

“The amount of money we could get from subletting is not going to change our future significantly,’’ Balter said last week as he sat in his glass-walled office. “But free space could be important to people starting out.’’

Alex Hsi and Douglas Jardine, two students at the Massachusetts Institute of Technology’s Sloan School of Management, are using their BzzAgent base of operations to build an e-commerce company. Veronica Chapman, who just earned a master’s degree in business from Babson College, is creating an urban youth service organization from her desk. For Alain Ferry, the free space has provided a valuable platform to launch RaceMenu, an “online network for cycling and other sporting events.

“Being in this environment breeds productivity,’’ Ferry said. “I have a problem working from home when the World Cup or the Tour de France is on. Also meeting potential investors here gives you much more credibility than a meeting at Starbucks or in your living room.’’

A few months into BzzAgent’s experiment, Balter has been pleasantly surprised. “Early on, we worried that we might attract squatters, people who just sort of hung around,’’ he said. “But the people who are here are not looking for a place to sit still. They are in transition. They are moving.’’

At Martini construction, the guests are architects; at BzzAgent, they’re beginning entrepreneurs. At LocaModa, a Cambridge mobile technology firm, two iPhone application developers and a pair of music software designers are working in a rent-free, unfinished office space on the first floor.

“Obviously, in this economy, we’re not lining the walls with engineers,’’ said LocaModa chief executive Stephen Randall. “Offering the space to creative people who don’t have a home seems to make the best use of the situation.’’

And the benefit is enhanced when the guests and the host company do similar work. “One insight from these guys could be worth $1,000 to us,’’ Randall said last week, as he stopped down to visit the fledgling businesses that are using his company’s donated space. “That’s why we bring them into meetings and bounce things off them.’’

The recession-driven glut of unused office space and the wave of office-less professionals are also feeding a new business model for Tech Superpowers Digital Lounge on Newbury Street. Originally an Internet cafe hosted by Tech Superpowers, an Apple computer sales and service company, the space was reconceived by founder and chief executive Michael Oh.

“Our Internet Cafe was always aimed at tourists,’’ Oh said. “But we realized that we could use it for something much more meaningful: to provide a good workspace for people who have been laid off or are starting their own business. There are lots of people building their careers or businesses who can’t afford office space or high-end computers - yet.’’

Oh has spent the summer converting the cafe into a workspace; starting Saturday, he is launching a selection of payment plans aimed at professionals plotting their next move. Monthly rates start at $30, and Oh is offering a free month for anyone who’s been laid off.

“The major benefit is the quality of the computers,’’ said Bob Doron, a designer who was laid off from Pearson Education last year, and an early user of the Digital Lounge. “I’m still designing book covers, freelance, but my home computer isn’t powerful enough to handle the graphics. The computers in the Digital Lounge, as you might expect, are very fast and very powerful, so I can bring my work in here and fly.’’

D.C. Denison can be reached at denison@globe.com.