Depends on how you want to start:See I don't recall this stuff being front and center, my experience with Greyhawk is you had to go out and find this stuff. Now I know, that's the point of D&D, but most other settings make it sound like the cool parts are out there everywhere.
Things like the spaceship or Dungeonland are kind of out of the way. It'd be like trying to say "hey, the Forgotten Realms has a land full of wizards with flying ships! ....though we don't have a sourcebook for it yet. Still working on the Sword Coast! But maybe in 6e!"
I had a campaign (a bit ago) start with a recently freed and still confused Iuz in giant form rampaging through the city of Greyhawk as he was making his way away from Castle Greyhawk.
The PCs (1st level) were mostly just trying to save as many people, things (and themselves) as they could. It was a fun introduction to the setting.