Right on, here we go.
Operating system: Windows XP
Network:
nbtstat
netstat
FastCache for DNS optimization.
PacketMon for packet sniffing.
HyperTrace for a better traceroute.
Security:
** Some of these I don't use anymore, but did for a long time
Port Mapper for when I didn't have a router and wanted to map ports that were abused to non-existent machines.
Port Blocker for use in conjunction with the above for blocking other ports.
Outpost Pro for my firewall before I knew how to configure the hell outta my router.
Misc:
Firefox - no brainer
Opera - no brainer
Cacheman Pro for memory optimization
Trillian Pro for my instant messaging
Atomic Time Sync for my atomic timekeeping
PerfectDisk for my disk defragmentation
AdAware - no brainer
Registry Cleaner to keep my registry clean of all invalid entries
Secure CRT and Secure FX for my ssh and secure ftp needs