NEW YORK ( TheStreet) -- Membership has its privileges, especially when it comes to scoring great travel deals.The latest wrinkle in the eternal search for a travel deal is the rise of private travel sales that offer deep discounts on luxury hotels and travel packages to members only in sales that aren't advertised to the public. They may be the ultimate tool for travelers who want to enjoy luxe for less. Discounts of 40% and more are not unheard of for luxury properties that have unsold inventory due to the sluggish economy or simply because it's off-season in their part of the world. Private, invitation-only travel deals bear some similarities to flash sales on airfares and hotel rooms that have proliferated in the past year or so on social networks and micro-blogging sites such as Twitter. But other than sharing an online provenance and having tight book-by dates, the two are very different. Unlike flash sales, which are open to anyone and cover a wide range of properties and budgets, private, invitation-only travel sites -- clubs, in a manner of speaking -- focus on the high end of the market. They feature posh, 5-star hotels and resorts that have often been vetted in person by the site's staff. Gilt-edged properties included in private sales in recent months include the W Hotel Barcelona, New York's Hotel Plaza Athenee, Four Seasons Resort Costa Rica and Aspen's Snowmass resort. Private sales typically allow wide windows for travel dates -- often months instead of days. Although private travel generates buzz by cultivating an aura of exclusivity, getting invited is actually not hard. The fastest way to join is by knowing someone who is already a member and have them invite you -- rather like joining a physical club. Otherwise, joining can be as simple as going to a popular site such as Jetsetter.com, TabletHotels.com, Ruelala.com or Vacationist.com -- a collaboration between Travel + Leisure magazine and LuxuryLink.com that debuted last month. You provide your e-mail address and state your interest in joining. There is likely to be a virtual queue -- part of the aura of exclusivity again -- so it will take longer that way, but you're highly likely to get in. Once you're in, you get frequent e-mail alerts about what's on offer. Memberships are typically free. Sales are first-come, first-served. Most sites mount a sale a week. Purchases are non-refundable.