How did you expand your newsletter?

At this point pretty much everyone knows how popular newsletters have become and marketers are preaching their value. I get the appeal - it's a direct connection to the inbox on daily / weekly / whatever cadence.

I have a few hundred emails on my site through signups to the actual application and from Survey monkey popups on certain parts of the site like our car show listing pages. These are purely customer acquisition channels and so I was generally ok with adding a form for those users.
www.topmarq.com/car-shows/tx

My problem is I don't really like having a popup like that on the rest of the site so I only do it there. Maybe I'm too particular but I much prefer a cleaner look for the user experience.

So, other than the popup forms on the website, how did you expand your newsletter? Did you find other creative ways or was most of the growth straight from online signups? If so, i may need to reevaluate my willingness to post to other parts of the site.

Thanks in advance!