1) yum
rpm automatic installer (help you to solve the tedius dependency problem by automatic download all the necessory rpms.

2) Novel Evolution Connector
This is for people whose company uses windows exchange server using the Exchange protocal (not pop or imap ).
For details -- http://www.novell.com/products/connector/

3) Perl

4) A list of security related tools
ethreal (your sniffer )
snort (your IDS tool, can use acid as the GUI)
nessus (your VA tool )
iptables ( your firewall )
nmap (your port scanner/OS finger printing tools )