Two rather excellent ideas for epic D&D campaigns have surfaced lately.
Sandbox campaign with an epic threat
Veteran RPG blogger Jeff Rients recently offered a simple formula for an epic sandbox campaign.
The idea is this: The player characters chance upon a single piece of the Rod of Seven Parts, one of D&D’s best-known artifacts. Fate bestows it upon them to seek out the other six parts and combine them to unlock the artifact’s full power. They rod is the only object powerful enough to defeat its own creators, a powerful extraplanar race who are returning to destroy or conquer the world they saved in ancient times.
The Rod of Seven Parts can have whatever powers the DM decides, or you could use the rules given in one of various sourcebooks (AD&D 1E DMG, AD&D The Rod Of Seven Parts, or other). A popular notion is that each individual piece has its own power, while certain segments when re-attached to each other unlock greater powers. The staff’s ultimate power can only be used when all seven parts are assembled, but the staff may shatter.
Fighting while falling through an abyss
Webcomic Penny Arcade are big fans of Dungeons & Dragons. For his 11th level epic battle, Gabe had his players freefall for several rounds while fighting, in an battle reminiscent of a similar event in Castlevania: Dawn of Sorrow. To accomplish this, he created an impressive diorama to enable 3D combat.
Gabe also posted his 4E house rules on freefalling.