Are you using spoutcraft as text can echo through the clients?, please be more specific on what plugins you use.
Seems to be coming up also in the Bukkit Devleopment section too with the console doubling its say command. TnT says it has to do with a certain plugin. Im not too sure though.
is there any way i can fix it one of the people on my server told me it was just on my computer EDIT by Moderator: merged posts, please use the edit button instead of double posting.
I should have been more clear. You need to seek out a fix from Spout. You can start by updating the plugin and see if that helps.