I run a similar website and it has just been my friends and I posting for about a year now (which is fine with us)...interestingly (and one of the coolest feelings I've ever gotten, I'm sure you can totally relate) somebody that I had never even heard of posted my website to yours last night and told people to check it out...Since then we've gotten about 200 signups (and 3-4 people that have been hanging out on there all day today).
Was it pretty quick after you launched reddit that you started seeing a ton of people using it? I had quite a while ago accepted that it would likely just be my friends and I posting on mine...