There are a lot of places where you can try to get validation for your idea. But before you start going to look for these places, get your Buyer Personas (the representation of your ideal customers) in order.
If you know who your ideal customers are, then the next step (of finding where they hang out) is easy.

You can easily start tapping into your (existing) social network, for example to try to find people to have a conversation with and try to find out if they're really having the problem you're solving.

Another place is local meetups, check out sites like meetup.com and see if they're meetup's in your area around the problem you're trying to solve. Go there and start talking to people!

Online, online there's million of possibilities to try to find your ideal customers and trying to get a conversation with them, use Twitter search, certain Facebook groups around your demographic, newsletters, things like Quora etc. to find people hanging around and trying to get solutions to the problem you want to fix. (there's a ton of online locations in this SlideShare deck if you need more inspiration: http://www.slideshare.net/jcvangent/doing-customer-development-and-stop-wasting-your-time-startupbus-edition)

Don't feel limited by the amount of budget you have, for having conversations with people you don't need a budget, you just need to know where to look to find the correct people to talk to. I recently wrote a blogpost around the subject as well, to give you some tips on how to reach the right people and what to ask them if you want to dig a bit further in the subject: http://inboundrocket.co/blog/stop-wasting-time-how-to-prove-youre-building-the-right-product/.

Best of luck!