I use the following tools for my auditing needs

A) System Auditing and Hardening (One time)

1) Linux Security Auditing Tool (Security centric,Text based output )

2) Dmidecode ( Retrieves info from BIOS )

3) Systeminfo ( Generates a nice html report)

4) Syssumm (Inactive since Oct 2000)

5) Rootkit Hunter (Does a basic config check in addition to rootkit checks)

6) CIS benchmarks

7) Bastille ( Interactive hardening and a security scoring tool)

B) Automatic Auditing (as a cron job or a service)

1) Logwatch

2) Psad

C) Remote Auditing

1) Nmap (Port scanning)

2) Nessus ( Remote Vulnerability check)

D) Wikipedia

1) System profiler

Any other tools/scripts which you can recommend?