Gentlemen, lower your toilet seats!
My dad brought me up to be a gentleman, and one of the things that includes -- if you share a bathroom with women -- is putting the toilet seat down after using it.
Bemis has made it easier to be courteous with their Slow-Close toilet seats, which lowers either or both the seat and the lid slowly and silently after you give them a nudge. You just start the seat closing, let go, and you're done.
We just moved into a new (to us) house, and we replaced the former owners' toilet seats with these right away. The convenience of being able to put down the toilet seat with so little effort almost certainly violates some chivalric code of required difficulty and sacrifice, but this is one of those small advances in modern engineering that deserves to become ubiquitous. If you have a reason to get new toilet seats, these are definitely worth consideration.
As a bonus, the seat also has quick-release snap hinges, so you can easily remove the entire seat for thorough cleaning.