Looking for PC case with side window.

I can personally recommend the Fractal Design R5 case.

Pros:
-Excellent cable management
-Lots of room for Hard Drives / modular HDD bays you can take out if you aren't using them
-Very sturdy case
-Quiet
-Dust filters on all intake areas
-Side window available

The only real downside to this case is that it is fairly heavy. If you plan on moving your PC around a lot this wouldn't be the case for you.

Here's a link to the case on Newegg: http://www.newegg.com/Product/Product.aspx?Item=N82E16811352049

For other recommendations it would be helpful for us to know what your price range is as well.

 
I'm using an NZXT S340, beautiful simplistic case with solid room for cable management and a large side window. The two downsides are that 1. the side window can scratch easily, I've never scratched it though, and 2. There is no optical drive slot. The front has a magnetic dust filter and it's easy to work with. For 70 bucks it's a solid case.
 
The Corsair Spec 03, you can never go wrong with this case http://www.newegg.com/global/uk/Product/Product.aspx?Item=N82E16811139040&cm_re=corsair_spec_03-_-11-139-040-_-Product , also you can check the Spec 01 http://www.newegg.com/global/uk/Product/Product.aspx?Item=N82E16811139041&cm_re=corsair_spec_1-_-11-139-041-_-Product , the Spec 03 is stronger when it comes to cooling, say the cooler master hyper evo 212 and water cooling systems, the Spec 01 on the other hand is a good well rounded case it has a decent cooling compared to the Spec 03 not the same of course but it's still good, so it really depends on your needs, and if it's a case window and good cable management all that you need then pick the Spec 01.