CheapTickets.com, for instance, e-mailed members this week with special discount offers tied into the holiday weekend, and is running promotions on its homepage.

"We're focusing on the fact that we're a week out from the holiday, and we want consumers to know we have these packages," said CheapTickets spokesperson Kate Sullivan, who said the site would consider a second mailing next week.

Trip.com followed suit with a similar mailing, offering savings of up to 60 percent on Memorial Day vacations.

Others, including Orbitz, sent out mailings after the major air carriers announced reduced fares for the weekend. Orbitz earlier this week distributed a mailing offering fares "as low as $74 round-trip."

"United [Airlines] initiated a fare sale on Tuesday that expires [Friday]," said a spokesperson. "Some others matched that sale, and it's part of our job to let consumers know."

Still other sites, including Travelocity's Site59, similarly launched time-limited promotions. The site, which specializes in last-minute getaways, ran a 24-hour sale that began on Tuesday.

The effort comes as much of the travel industry is looking to vacation season to help reverse its fortunes. Yet with increased security procedures, heightened labor tensions, and major financial woes facing many of the major carriers, many believe that travel next weekend and throughout the summer is unlikely to prove much of a panacea.

That's on top of reports by groups like the AAA (formerly the American Automobile Association) that air travel will be sluggish during Memorial day -- down 7 percent from last year, to 4.1 million.

Despite the pessimism, not all travel sites are pessimistic. Those that offer not just combined airfare and hotel offerings are especially upbeat, even though auto rental and hotel deals often are less lucrative than air travel packages.

"We have options that don't include air travel as well," said CheapTickets' Sullivan. "Whether they're choosing to fly or drive, we have both ... so consumers will still be able to have options with us."