"Often enough" varies significantly by age and disposition.
We're on our 9th year educating an introverted social butterfly who also happens to be an only child.
DD13 is (mostly) content with her social life, though we have another constraint that makes socializing a nightmare-- or did, anyway, when she was younger. We didn't have as much social exposure as other parents probably feel is "necessary."
But we're a family of introverts and loners, to some degree.
Places that we've found social activities for DD:
Library programs
park district programs
local athletic clubs that run daytime kid's classes (those kids TEND to be homeschool kids)
art classes
music instruction (group lessons)
4-H.
Obviously, a house of worship is also a great place to meet other people. We've expanded DD's social circle tremendously by encouraging her to do a lot of community service in the past couple of years.
