[thenomad]

HN throws about 20k - 40k visitors over a day or so, in my experience (off the top of my head, without looking at stats). My stuff tends to be tangential to the primary interests of the userbase, though, so if you were very codey / techie you might see a lot more.

Reddit depends wildly on the size and activity of the subreddit you're featured on. Imgur shows view stats, so you can get some idea from that.

For scale on whether nginx can handle that sort of load, I've had tiny VPSes sitting there happily handling 200 SIMULTANEOUS users serving static files, which translates to between 500,000 and 3 million uniques a day, maybe more depending on your site design.