How did you market this to get that many visitors?

Well, for one, it's a very very common question here on HN, nad I can't think of a time I've seen the question asked that he hasn't helpfully responded pointing out his site, which has lots of answers to the exact question people keep asking.

It's really a win/win, and because he's sincerely answering the questions, it doesn't come across as awkward of misplaced self-promotion.

I actually launched my side project on indiehackers - http://www.oppsdaily.com - a newsletter filled with software opportunities. I posted some of the traffic stats here http://www.oppsdaily.com/blog

I just signed up for versioning newsletter, all I did was pit in my email and I got a quick confirmation.

I also signed up for oppsdaily, but the verification with MailChimp was quite difficult. I had to select pictures with grass, then select images with house numbers, then select new images with house numbers. You might want to consider using a different provider.

This is Googles captcha system and its used by a bunch of services. It has nothing to do with Mailchimp (except that they use reCAPTCHA) so changing mailing list provider for this might not be a wise idea.

With that said, I much rather prefer this new reCAPTCHA compared to their old version with hardly any readable characters.

This may be the first time I've deliberately signed up for a newsletter. Great idea.

This looks really cool. I signed up.

Wow, thanks so much! I hope you find it useful. :D

As kowdermeister pointed out, lots of the visitors come from Hacker News (~50%). I figured the site would be popular here based on the popularity and regularity of threads like this one! Since launching, I've continued to submit one new interview from IH to HN at the end of each month, and they usually make top 3 on the front page.

Hacker News probably did the majority of the seeding.

In the blog section of IndieHackers he talks about this. Primarily HackerNews. It's a good read.

How do you monetise?