We are in 3 secular homeschool groups. Sonoran Desert Homeschoolers, SOARing Unschoolers, and Northwest Tucson Homeschoolers. Our kids are 6.5 and 4 in August. We live near the university.
Most of our closest homeschool friends are also in all three groups. However, we are all most active with NWTHS http://nwths.webs.com/. Most of the kids who go to park day are 10 and under. It's a nice, eclectic group. There are several families that follow curriculums, but most I hang with are on the life learning spectrum. We meet every Tuesday at a park on the NW side of town.
SOARing is a very active group with lots of getting together to just hang out activities. The kids are just a bit older than mine so we don't do so much with them.
SDH doesn't have quite so many organized activities. Park days happen on Tuesdays during the school year at centrally located parks.
This summer Kino Learning Center is opening their school to homeschoolers so we can have an air conditioned place to get together. Cost is no more than $10 per session for two or more kids, though if you have one child or pay in advance it is less. You can pm me for more specifics. This is not babysitting, it's just a place for the kids to play in with parents on site.
Fridays at 11-12 is open gym. $15 for annual gym membership and $5 per session per child. Again, pm me for more info.