StealthLogin is a plugin that allows Administrators of craftbukkit servers or anyone with the permissions node for that matter to login without being seen.

It has only one known conflict, MCMA. Just disable welcome messages in the MCMA configuration to resolve this issue

The permissions node to make this work is

    stealthlogin.quiet

This also works if you have the permission node *, so be careful.

The plugin can be downloaded here http://jenkins.craftrepo.com/job/StealthLogin/3/artifact/StealthLogin.jar (wget), and will work with craftbukkit 580+.