We utilize the umbrella Group called Many Paths of Natural Learning. It is a state-wide group and is on the state's list of approved umbrella school (I checked.)
It is very unschooling oriented/friendly, but also very curriculum friendly. Basically, IMHO, it is very 'what works best for your family' friendly.
There is a yahoo group with the same name, but that is not the same thing. The yahoo group is used by umbrella group members and non-members alike as a networking and planning resource for homeschooling activities all over Maryland. In order to be officially registered with the umbrella school you have to fill out some paperwork and enroll. There is a one time enrollment fee for the family, and then yearly tuition for each enrolled child ($175/year for the first child, $20/year for each additional child in the same family.)
You do a pre-enrollment phone interview and then are required to go to at least one 'signing event' sometime during the year at one of the many, many field trips that are organized and posted as such. At the end of the year (if I understand this correctly, since this is our first year here in MD) you submit basic paperwork indicating some of what you/your children did during the year.
I like that Many Paths does not require any specific type of religious education...or any specific type of any educations, religious or otherwise. It is completely inclusive of all religious beliefs -- including none at all.
By enrolling with Many Paths, and making sure we fulfill the minimal requirements, we are completely fulfilling the letter of MD's homeschooling laws. For me, with not knowing whether or not a school representative would be unschooling-friendly, this takes the stress out of homeschooling here.
I am not at a computer with my links, but if you do a google search I'm sure you can find both the yahoo group and the main website for Many Paths. We had a conversation/thread with it recently too, where LotusDebi and I were talking about it and I'm pretty sure I had a link posted there. I'll go see if I can bump something up.
As for my 'con' I have found that it's quite doable. I have three children (9, 5, almost 2) I get necessary alone time during the baby's nap, during which time the boys play together on the computer or with whatever strikes their fancy. I can hear them and I know that they are basically trustworthy (well, not the 5yo, he'd jump off the balcony thinking it just seemed fun...that's why we take turns keeping an eye on him...) This has been my salvation/sanity. I get about 2 hours where I can have my own thoughts...I can work on crafts or think or journal or just veg-out without 3 million why questions and the boys get a break from my constant supervision.
I also keep connected to my inner-state and make sure that I get to go off to the grocery store or errand running alone when I am feeling depleted. DH knows that it's best not to disagree when I say I NEED some alone time.
Somehow we make it work and we are all happier because of these choices.
Once we can get out of this tiny, yard-free, apt, we'll be happier and can achieve balance more easily...but for now...this is what works.