In session 9, Tyrriel and Wilhelm both used Sleep scrolls that they had made several sessions earlier. I use the rules regarding scrolls from the Basic D&D rulebook edited by Dr. J. Eric Holmes (the edition that preceded Tom Moldvay's edition that we are using in this campaign).
In most editions of D&D and AD&D, you have to wait until you are 9th level to create any kind of magical item. Dr. Holmes allowed magic-users to create scrolls of spells that they know any at level, at a cost of 100 gp and one week of game time per spell level. This is unique among D&D editions, and is definitely not by-the-book for the edition we are using, but has become a fairly common house rule among modern "old school" campaigns. I generalize the rule to allow any spellcaster, including elves and clerics, to create scrolls.
The one important proviso that I add is that scrolls created this way are "personal scrolls" and cannot be used by anyone else. They are a sort of shorthand mnemonic for a spellcaster's own innate magical powers, and will not function for another caster, nor can they be used to assist in spell research. This prevents PC or NPC casters from selling cheap scrolls on the open market and making it too easy to get access to new spells.
I really like this rule, as it gives 1st level magic-users and elves a little bit more to do, and a way to spend some of the money they have been accumulating as they climb towards 2nd level. So far it hasn't unbalanced the game (anymore than the "insta-win" Sleep spell already does, at least).