A good point by Jake, get them to signup for your newsletter, monthly or however, through which you can reach out to them.
Plus, being on social media, you can start working with infographics and promotional videos. They would get a lot more shares and you'll in return get a lot more traffic. You have done giveaways, which is awesome. Now you can hold some little competitions, like build your site a logo or design a homepage midway banner or you could have them write about what they like about your product and you could promise to have that on the main page and this could also be a monthly competition or so, so the one chosen best gets to be on the website. You could offer the similar with audio or video or picture of voted user to be on the site, or be included in the newsletter. What you'd be doing is promoting input and also sharing on social media and emails by your audience without having to do anything yourself.
Since you are certain you have a good fan base, why not start doing meetups etc. Reach out to them more publicly. You have no idea how much of a boost this off-the-net event could be for your web presence.