After seeing one person post some memory modifying method to lowering ping I figured I would post the one that I know to work.
Before I continue - I certainly hope this isnt a repost as I searched lower ping and didnt see anything.
First - Download and install Fasterping - Faster Ping | World of Warcraft Tools | Curse
Its clean - no malware hidden.
After the install - obviously run it.
Set the TcpAckFrequency to 1 -check the yes bubble <- any questions - refer to the picture below.
Turn off Nagle's algorithm - check the yes bubble
Click apply changes (if you are running vista you will need to follow their directions on what to do before you apply changes. I run xp on this computer so I don't know whats added)
Restart your computer and check out your ping. Mine dropped on the Sargeras server from 164 to 84. Noticeable differences in my rogues abilities ensued - from more precise kicks to faster shadowsteps.
Enjoy