My general sentiments are that sex is an extension of touching, therefore a potential form of communication, therefore "sacred", and as such, should be practiced, in caring forms, at every reasonable opportunity, with any cooperative person or persons (as long as it doesn't interfere with other, more critical forms of communication). If this isn't "making love", it's at least a very nice kind of masturbation.
It's all in the Chemistry, a parable comparing atoms and molecules to people and groups.
Guidelines to "Intercourse", comparing those for different kinds of "intercourse".
Practical aspects of Communal Living
Mutual Social Auction
An idea for a Meet Market, rather than a Meat Market