I'm already publishing a weekly "trading post" that could surely use support, so definitely interested in #1.

#5, parenting tips is always good. My past neighbour ran a small day-care and had lots of techniques for raising children that worked quite well. I learned a lot from her. She managed to turn around some fairly difficult cases using her techniques. I'm always willing to share anything I know.

One that isn't on your list is a gaming community. There are already a few of them, but none of them have real clout to bring everyone together.