Try changing color. Maybe ads are too much blend so visitors don't notice them. Try making them stand out from page. You should get at least 10 clicks for that traffic though yr niche is not a high paying one.
Don't expect much for 600 UVs per months. You need to do more SEO to improve your serp rankings for more traffic.
I'm no guru but heres some things that have helped me. Write some more unique content and do your keyword research using google adwords keyword tool. more content = more chance of traffic Unique content = google likes you, get better serps and indexed quickly When you've finished writing content optimize it for that keyword. 1) check keyword density 2) check for keyword in H1 H2 tags 3) Check keyword in meta tags Submit content to 1) social bookmarking sites 2) sites like digg, reddit & mixx 3) get relevent back links from other sites 4) Submit to directorys 5) Link building - blog commenting not spamming 8) submit site RSS feed to directorys Like I said i'm no guru but i was in your position and was told the above by DP members and now traffic has improved alot. Best of luck
600 visitors a month is not that much, your placement is good though. Also keep in mind that if the majority of your visitors comes from digitalpoint, then you have a majority that are ads blind.
Try posting articles(original) in those websites where adsense earning is shared with the webmaster.Put your adsense id there,when anybody clicks adsense ads beside your article you will be credit with the commission.The best part of this advise is that you dont need to think abt bringing traffic to your articles as they will be automatically indexed as they are placed in a site with good google PR.
Traffic is definitely low, but even with this much traffic you should get a few clicks. I don't think the placement is right. I had a quick look, and I feel you should add ads on right above that 'Random Pen Pal' thing. You should also try using link ads, you how they work for you.