I turned 50 last December, and went to Rancho la Puerta near San Diego for a week by myself. Heaven. My best friend turned 50 this year, and we are going on a trip to Turkey and Greece together in October to celebrate turning 50 and our 32 years of friendship.

Here is a link that might be useful: Rancho la Puerta

I haven't done an organized program such as you mention but highly recommend doing something special for yourself that is of interest to you. It's great for your self-esteem and to reduce stress. I have 2 friends I've know "forever" and we go to a hot springs resort for a couple of days 3 or 4 times a year. We thoroughly enjoy relaxing in the hot pools and catching up with each other's lives. We walk the lakeshore, shop, eat, and laugh a lot. Worries and our regular lives are left behind for those 2 days.

Turkey and Greece! Wow!
I went to Key West with two friends last spring for 4 nights and it was heaven just to have all that unscheduled time. I usually go away with friends maybe 2 different weekends per year and love it. Getting 4-5 days is a huge deal because DH's work schedule is not very flexible and my youngest is 12 and needs rides to/from school and activities. I'm in New England so going as far as CA is probably not an option. I'm not sure if any of the dates/locations will work for me (and a few friends) to go to the camp above, but I definitely want to do something special.

All suggestions welcome! Preferably within driving distance or within a 2 or 3 hour flight from Boston.

A couple of years ago a close friend who was turning 60 organized such an experience. She teamed up with another friend who was also having the big six-oh day, and each invited a set of women they knew. Turned out that my friend's cohort was just me and one other woman and the other person ended up with her sister, her SIL and a group of five other friends. But we all had a fabulous time!

We spent a week out west and visited Bryce Canyon and Zion National parks. The birthday girls, er, women :) organized everything including hotels, outings and a nice combination of group meals and chances for folks to split off if they wanted to. We hiked the Virgin narrows one day and a stunning slot canyon route another, we rode horseback, we zip lined. We stayed in two places, and one was a full service spa so people had the chance to do whatever pampering was desired.

I was nervous about going; I'm rather a stick-in-the-mud and as mentioned I really didn't know most of the group which ended up being a total of 11. However, I am SO GLAD I went! I challenged myself to do things I never would have tried on my own and it turned out that the group included a truly amazing collection of smart, accomplished and fascinating women. We literally had a doctor, a lawyer and an indian chief (ie successful entrepreneur). There was a psychologist, a financial advisor, a botanist. Our talks over meals or during hikes were so enlightening.

Since we ended up an odd-number group I was happy to 'volunteer' to stay alone rather than being assigned to double rooms which is what everyone else did. Having space of my own was ideal for me, I need alone time and at this stage of my life the extra expense to have a room to myself was well worth it.

My other experience in that vein was last summer when I rented an extra week at the beach house where I always go with my daughter for our summer getaway, and invited my sisters to come for a few days before my daughter came over. That was nice too, just us with nobody responsible for spouses, kids, etc. There are five of us and although my youngest sister couldn't get away, the rest of us had a very nice time.