The NetScaler from Citrix, is a networking product with more than just one use case.
Personally I´ve not had the pleasure to dive really deep into this yet, so usually just end up with some normal setup for XenDesktop/XenApp use cases, som url rewrite other stuff like that.
But I really would like to get the change to work more with this product as a whole.
The capabilities and use cases are so many, and with all the editions and licenses available, you can be sure to find one for your need, whether its an virtual appliance (VPX), og a physical NetScaler for the heavier loads.
Now, for som general information regarding the NetScaler I found this blog post, which contains some good information around the product.