Is a user under 500 posts allowed to create an Unofficial group? I know my post count is quite low to be a lead of a group, but I have good intentions.
Unofficial, yes.
A few other members have recruited with less than 500.
Just remember this cannot then be made into an official group with their own Userbar etc.
What group would you like? If it's appropriate a member with over 500 posts may make it.
You could make it then when you reach 500 posts you could try and make it official, or you could get another member to lead it like Untouch said.
I actually have ideas for a few groups.
One, being a Musical Group for those who are entertained by Music.
Second being a tech-savvy group.
There is already Geek Squad.