Definitely have an internet addiction, and I've gone through a sort of withdrawal more than once when I had to go months (or one time, a few years) without it. Though I'm generally fine if it's only a few days or a week or two without it, provided I have books to read instead.
Also somewhat addicted to buying books and sex toys, though I've been getting better with that lately. After my wisdom teeth were removed, I almost got addicted to painkillers.