ASS, the autonomous system scanner, is designed to find the AS of the router.
It supports the following protocols: IRDP, IGRP, EIGRP, RIPv1, RIPv2, CDP, HSRP
and OSPF.
In passive mode (./ass -i eth0), it just listens to routing protocol packets
(like broadcast and multicast hellos).
In active mode (./ass -i eth0 -A), it tries to discover routers by asking [...]

What is Nmap?
Nmap (”Network Mapper”) is a free open source utility for network exploration or security auditing. It was designed to rapidly scan large networks, although it works fine against single hosts. Nmap uses raw IP packets in novel ways to determine what hosts are available on the network, what services (application name and version) [...]

Here is p0f “sales pitch” from it’s website.
What is p0f v2?
P0f v2 is a versatile passive OS fingerprinting tool. P0f can identify the operating system on:
- machines that connect to your box (SYN mode),
- machines you connect to (SYN+ACK mode),
- machine you cannot connect to (RST+ mode),
- machines whose communications you can observe.
P0f can also [...]

Nikto Homepage: http://www.cirt.net/code/nikto.shtml
Description: Nikto is an Open Source (GPL) web server scanner which performs comprehensive tests against web servers for multiple items, including over 3300 potentially dangerous files/CGIs, versions on over 625 servers, and version specific problems on over 230 servers. Scan items and plugins are frequently updated and can be automatically updated (if desired).
Nikto [...]