[buug] recommendations for network security tools?

[Bob Read]

Hi,
   I'm looking for recommendations for network security tools:

1)  subnet scanning and IP discovery (nmap...discover new IPs and categorize them with port scan)

2)  corporate environment windoze workstation monitoring (to identify a windoze box that has been owned via netflow/sflow, virus scan, port scan, etc)

3)  secure linux environment (for PCI compliance, for example)