March of the Sane is one of the original Dungeons & Dragons adventures released in PDF format on the Wizards of the Coast website as part of a quasi-monthly series. Intended for four 5th-level characters. Uses the version 3.5 rules,but it can easily be adapted for use with the 3.0 rules as well.

From the website:

Billing themselves as Places of Sanity, small towns all over the realm have begun turning away adventurers. All over the region, inns, taverns, shops, and even private homes have begun turning away adventurers. "No heroes," say the signs on the doors. Shortly thereafter, these same towns are found razed to the ground -- looted, burned, and empty of life. What evil is causing whole towns to forswear not only heroes, but also their normal defenses

Drop the latest miniadventure for D&D v.3.5 by Owen K. C. Stephens into any spot in your campaign world that features a roadside tavern. Suitable for four 5th-level characters.