D&D House Rules

The following house rules are (mostly) standard for my D&D games, although some of the more unusual may be marked as optional even in my stuff. Get me to list the variants I'm using before a game begins.
Small variations (or those that didn't need much explaining) are in the first section; others get pages to themselves. If I'm running something that isn't online, you can either expect me to bring (or otherwise make available) a print-friendly copy, or I might just remember the changes and not bother letting anyone else look at them.