It's really tough for me to claim the "old school" mantra for pretty much anything relating to gaming, seeing as how I picked up my first game book in 1995 (Star Wars d6, 2nd ed., revised & expanded). That's hardly old school. But looking back over my comparatively brief gaming career, I was out front in at least one trend: collaborative worldbuilding.
Games like Burning Wheel and Shock make a lot of hay over the opportunity to sit down with your buddies and build a complex gaming world from the ground up, and rightly so: It ties the players intimately to the setting and equips them (early on) with the tools they need to push the story forward.
For me, the opportunity to try this out came in 2002. I was in college at the University of Missouri and my local group was jonesing to try out Silver Age Sentinels, which most folks remember as the precursor to Mutants & Masterminds. At the time, we wanted a setting considerably darker than the Silver Age fare offered up in SAS. (Really, we wanted to play Watchmen.) We started tossing around ideas for the ideal setting, and before too long we were caught up in a full-blown collaborative worldbuilding effort.
The result was the world of the Sovereigns, a hard-edged team of supers who mixed 21st-century sensibilities with the heroic ideals of times past. I'm going to start posting bits and pieces of what eventually came to be known as our Sovereigns Sourcebook. It'll be tagged "Sovereigns," for ease of searching. Look for more over the weeks and months ahead.