Ask HN: What do in months after graduating?

I'm graduating early and have a job at a top company lined up, but I don't necessarily want to start right away. It's getting late, but I'm hoping there's something I can do to enrich myself before I enter the workforce. Does anyone have experience with this or any ideas?

(I know 'travel' is the obvious answer, but that wouldn't be very fun alone, and at most it'd be a couple weeks)