Managing Lots of IP Addresses?

haggisbrain asks: "I'm a Systems Administrator and I've recently started work with a new company where I'm now helping to support a much larger number of nodes than I've previously supported. We have just over 1000 nodes to support, but no efficient method to manage the IP addresses and subnets used. Previously, an Excel Spreadsheet has been sufficient enough for my needs, but now I need to find a new way. Can someone recommend a piece of software which can help me? Is there a simple way to list and view the IP addresses used on my network?"