I love reading the gaming ideas on OSR blogs, but among the many fine ideas presented only a few immediately strike me as something I know I will use in my games. Telecanter posted such an idea today: Summon Library.
A magician casts a spell that summons something bulky, awkward, and incredibly useful at that precise moment. What things would you want to summon? An alchemical lab, a troupe of actors, a font, a barge, a forge?