There are a number of free ways to grow your audience for free but my favorite is Entrecard. I'm sure you have noticed over there on the right, the site of the day. That's another member who has chose to advertise on my blog. Each time you click on their avatar they receive a credit to their account.
Yes it's free but it's also fun dropping your "business" card at each other's sites and then you get to choose whose site you wanna advertise on.
I try to do it daily, but always don't have the time and that's ok with Entrecard.
I've met a lot of really nice people that have great sites. If you would like to join us (sign up is quick and easy) just click this banner and I will get a referral too!