A very simple and lightweight bukkit plugin that automutes the worst spam, and lets OPs do /mute.
/mute <player> [minutes]
- Mutes for [minutes], 0 minutes = forever and is default. Can only be used by OPs.
/unmute <player>
- Unmutes . Can only be used by OPs.
/amimuted
- Tells you whether you're muted or not. Can be used by all players.