What to post:
What NOT to post:
Subdomains not interesting enough to warrant its own post.
Aggregators
Something all of the internet probably already knows about.
Something not unique.
Sites that serve as something that has been done to death over and over again and most people here have probably already heard of. (i.e, facebook.com, netflix.com)
If you exhibit a similar addictive lust for information as you do for internet, we highly recommend you go give /r/dataisbeautiful a sub too.