The Inform 7 site now hosts a new extension of mine, Permadeath. This extension implements rogue-like saving. What does that mean? It means that (1) the player can save the game whenever he or she wants, but saving immediately results in quitting the game; (2) every saved game can only be restored once; and (3) when the player dies, his previous save game becomes unusable. In other words, you can only save to "pause" and then "resume" the game, but you can never use it to undo something that has happened. This makes for very tense games, as (to name one obvious example from which the extension gets its name) death is final.
Obviously, this extension is not to be used lightly. Think long and hard whether your game will become more fun by adding this feature, or whether it will only become more frustrating.
The extension also allows the author to switch at will between "normal" and "permadeath" saves. As a somewhat classic example, you can have a town where the player can make normal saves, which can be restored without limit and independent of whatever happens to the character afterwards; and a dungeon where you can only make "permadeath" saves which will become unusable after restoring or the death of the character. This allows you to fine-tune the balance between good tension and bad frustration.
Because it uses an external file to write down data about the save games, this extension is Glulx only.