This is an advanced technique and should only be attempted by people who know what they are doing. This involves registry entries. 3rd Fleet will not be held responsible for any possible incurring damage caused by inexperienced users. (Brex won't be either)
This has a high tendancy to slow other games down as well as internet services. First of all backup the registry (this should be common practice for any registry tweaks) and then set a restore point. Enter regedit into the run box and navigate through to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Servic es\Tcpip\Parameters\Interfaces\'. You should now see all your network cards listed here. Find one with your IP details in the right hand pane and right-click. Add a new Dword and call it TcpAckFrequency right-click that and give it a value of 1, setting it to 2 should restore it (0 will probably disable your internet all together, this is bad, don't do it).
Then find 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSMQ\Parame ters' and create a new Dword called TCPNoDelay. Give that a value of 1 and reboot. Vista users may have to install MSMQ first by using the Control Panel\Programs and Features\Turn features on and off.
This was tested using WoW and Dalaran and the original ping was 108ms, now down to 31ms. Of course the speed of your actual internet will matter with this. If you're still running off a 28.1kb/s line... this isn't exactly going to help you out.