I think Occult Moon's "Toys for the Sandbox" series is a good idea. At .99, this 4- page pdf (which includes the cover) provides a nice, system-neutral, scenario to drop into an ongoing campaign. Plot hooks are provided for an aspiring GM to develop as he or she sees fit. Main NPCs are also given some personality and fleshed out somewhat, although not with any stats.
As a GM with a bit of experience, I could see myself using this as a mini-encounter distraction for players. The format provided can also provide inspiration for a GM to develop their own encounters. Worth every 99 penny!
[4 of 5 Stars!]