Sorry it was a hit and run post but I knew others would fill in.
As explained being part of one of these groups bring insurance and in some cases even medical insurance.
4H is traditionally for things like farming and home arts but they have really branched out. As mentioned several FIRST teams are 4H.
http://4-h.org/
As Kara mentioned Venturing is the young adult, co-ed part of Boy Scouts. It is mostly about the outdoor experience but many scout councils will allow more tech-ed focused groups. Exploring (Learning for Life) was part of the BSA but was spun off from scouts. Many scout councils also offer Exploring. Contact your local scout council to see which program could be appropriate and what benefits being part of these groups can bring.