Well in your price range, you just need a great performing laptop in general. Here's a laptop with an i5 Intel Processor 4200U ("U" meaning it's less powerful than the "M" range processors because of its focus on energy efficiency).
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http://www.amazon.com/Acer-E1-572-6870-Processor-Window...) - $461.59 & FREE Shipping.
If you want to spend about $20 over $500, you can get an i5 Intel Processor 4200M, which is much more powerful and catered to CPU-intensive programs.
The integrated Intel graphics should be fine for development, unless you're going for a graphically-ambitious game!
Let me know if you have any questions!