Recommended Net tools

I am starting a new position and would like some input into what the best net admin tools and wht the best net processes are to use in the beginning. It has been a little while since I was doing serious net admin and I want to quickly be able to identity IT and Network inventory, build a topology map and be able to some monitoring of Windows NT or 2000 servers and all network devices (Cisco). Does anyone have good input as to what easy and cheap tools to use?

Plus any other recommedations?