TeleportEffects is a Bukkit plugin that intercepts every teleport and re-schedules it while creating some particle effects on the start and destination points.
This is a page presentation for the plugin, if you are looking for the Wiki
you should go here.
The reason why I created this plugin is that I have seen various custom projects that create these type of effects, but not for every teleportation:
some only implement this for teleport between players (/tpa) while others only for movement to certain destinations (/warp).
TeleportEffects tries to generify by piping every teleportation through its filter.
This gives a more uniform look to your server, making the audience assume that all kind of teleports are handled by the same plugin.
Since TeleportEffects does not know if the cause of a teleportation is a command, and even so it cannot know what messages the command is going to send to the player,
I suggest that you disable any message sent from teleportation plugin.
If, for example, a /spawn plugin sends a message to the user when they reach destination, you should make the message blank ("") and leave the text part only to TeleportEffects
(check out the messages.yml file).
Do keep in mind that using TeleportEffects is not 100% secure, and it might cause some problems.
Check the dedicated page in the Wiki for more.