The philosophy behind donation-based yoga is accessibility: making yoga available to all people, regardless of fitness level or finances. This makes for a refreshingly un-elitist and welcoming atmosphere, where you can loosen those stiff muscles without feeling ridiculous. A seemingly haphazard business model, studios of this type are gaining in popularity, for obvious economic reasons. Suggested donations range from $5-20, and drop-ins are always welcome. You can generally look for a well-situated tissue box to drop your dollars in.

Read on for a list of donation-based yoga locations in the United States.

Leader of the pack, Yoga to the People is based in New York City’s East Village, with satellite studios in Berkeley and, now, San Francisco’s Mission District. Classes are a mixed-level Power Vinyasa Flow, where the focus is on breath and body awareness. Instructors play music from their own iPods, everything from Joy Division to Nick Drake to Outkast. Perfect for the traveler, rental mats are available at a reasonable $2.

Los Angeles’ heavenly weather makes year-round yoga-in-the-park possible. The folks from fire dancing school Fire Groove host a daily outdoor yoga class, with an additional Sunset class during the summer months. Bring a mat or blanket, and Warrior 1 in the warm California sun.

Up the coast, Portland’s integrative-health-and-fitness-center-in-one Kaninga has added donation-based yoga classes to its repertoire of wellness. If that doesn’t get your Qi flowing, try a low-cost DaoZhen Body Work Clinic (phew!).

Always-funky Austin has gotten on board the donation train with the opening of Black Swan Yoga. Classes range from Power Yoga to Hatha Flow, and the convenient Downtown location means there’s no excuse for not busting a bridge pose in the Lone Star state.

In the windy city, Yogaview Division serves as Chicago’s only donation-based studio. Dead-center in the bustling Ukrainian Village neighborhood, the studio’s back patio makes for a wind-sheltered post-yoga kick-in spot. Classes are divided into three levels. Most fun? The whatever-goes Freedom Style class on Thursdays.

Venturing further off the beaten path? Donation-based yoga studios aren’t just a big-city thing anymore. Check out Yoga by Donation in Portsmouth, New Hampshire; Rubber Soul in Athens, Georgia; and Yoga Energy Studio (YES) in St. Petersburg, Florida.

[Photos: Barefoot yoga: lululemon; city yoga: lululemon; beach yoga: Carnaval King 08, half dome yoga: lululemon, all Creative Commons]

Aspen, supremely gorgeous in its own right, becomes exponentially more good looking during the winter months as stars descend on this winter playground.  Jack Nicholson and Kevin Costner are mainstays of this chi chi mountain village, and Mountain Mama over at Traveling Mamas ran into Seal and Kyle McLachlan while skiing with her family at Buttermilk Mountain. A celebrity winter escape isn’t just fun and games, however, the celebs also try to get their philanthropy on. Every year, the rich and famous strap on their skis and boards to raise money for the Aspen Youth Experience during the Aspen/Snowmass Celebrity Downhill Weekend. Here, stars partake in a variety of semi-competitive events such Fastest Celebrity Racer (Chad Lowe in 2009). Participants in this event have included Dave Navarro, David Alan Grier, Judge Joe Brown, former NBC bigwig Ben Silverman, and former Superman Dean Cain (pictured above on the slopes). The event occurs in February, so be sure to book your rooms at the popular St. Regis early.

When celebrities need to get somewhere sunny, sexy, and celebrity-friendly, many head to the Bahamas, where warmth, sand, and privacy are a given. Tiger Woods, Eddie Murphy, Mariah Carey and husband Nick Cannon all reside here.  When the Atlantis Resort in Nassau opened its latest property, The Cove, in 2007, Magic Johnson, Cindy Crawford, and Tyra Banks (among others) bought up space in the all-suite, adult-only hotel to party the night away. If you weren’t able to make the little get together, you can still be pampered like a star at The Cove’s Mandara Spa, 30,000 square feet of relaxation and ‘delicate waterfalls’.

Marathoners in London

If patting yourself on the back after out-pacing the ingenue of your choice is more your style, consider participating in the Flora London Marathon, a veritable treasure trove of sweaty, achy, red-faced celebs running for their favorite charities. The Guardian chatted with Katie Price and Peter Andre about their training schedule (when they were together, of course ) about their grueling training schedule for the 2009 London marathon to raise funds for Vision, their charity of choice. Also racing that day was foul-mouthed Chef Gordon Ramsay.

Seen a singer sweating out last night’s soiree at your hotel’s gym? Run into a director while racing across Paris? Leave your Celebrity fitness sightings in the comments.

[Skiing photo: Aspen Youth Experience, Marathon photo: corono / Creative Commons]