Visual Network Diagramming/Configuration Management/Documentation tool

Our network is becoming more and more complex with interactions between applications on different servers and I need an efficient means of documenting my network/server configs so I can quickly determine those interactions when making changes.

I'm looking for a product that will allow me to visually diagram/document my network.  Ideally the product will be something like Visio where it will present me with a visual layout of my network and let me drill down to individual components so I can document configuration information such as hardware and software applications running on a particular machine.

Does anyone have any suggestions regarding tools they've used to do this?

Thanks