Bukkit

ScheduledAnnouncer is an inactive plugin, but there is an fork which is still active. Have a look at ScheduledAnnouncer 2.

Scheduled Announcer is a very simple tool, which only does what's its name told us. It automatically sends a broadcast out of a list controlled by a scheduled.

Features:

• Sends Scheduled Broadcast to all Players
  
• Easy to configure by 'config.yml' or ingame with the '/announce' command.
  
• Supports colors (&1, &2... &9, &a, &b... &f) and newlines with &n.
  
• Supports executing commands inside Announcements. (Like "Now it will get day!&n/time day")
  
• Supports newest Bukkit permissions system!

Setup:

1. Download the latest Release
   
2. Upload it into your plugin/ directory
   
3. Restart or reload your server

Or have a look at the Video Tutorial by BrandonHopkins

Configuration:

#
# ScheduledAnnouncer Configuration File
# =====================================
#
# Don't use tabs in *.yml file!
#

announcement:
    # Use this flag to temporary disable the announcements.
    # enabled: false, means that there wouldn't be any announcements.
    enabled: true

    # Set this to true will announce in random order.
    # 'false' will announce in sequential (one after another) order.
    random: false

    # Defines the prefix for the announcement. Use & + hex char 
    # for color codes.
    prefix: '&c[Announcement] '

    # The time of one interval in seconds.
    interval: 100

    # List of messages to announce. You could use color codes by
    # using & + hex chars too. &n will produce a new line.
    messages:
    - 'This is the first default announcement!'
    - 'Use /announce help to get info how to config this plugin.'
    - 'You can also configure this plugin with its config.yml too!'

Commands:

/announce add <message>

Needed Permission: announcer.add Adds a new announcement with the Message: <message>

/announce broadcast [<index>]

Needed Permissions: announcer.broadcast Broadcast an existing announcement NOW.

/announce delete <index>

Needed Permissions: announcer.delete Removes the announcement with the passed index.

/announce enable [true|false]

Needed Permissions: announcer.moderate Enables or disables the announcer.

/announce interval <seconds>

Needed Permissions: announcer.moderate Sets the seconds between the announcements.
Calling it without an interval to set will return the current interval.

/announce list

Needed Permissions: announcer.moderate Lists all announcements.

/announce random [true|false]

Needed Permissions: announcer.moderate Enables or disables the random announcing mode.
Only calling /announce random without true or false, will return current mode.

/announce reload

Needed Permissions: announcer.admin Reloads the config.yml.

Permissions:

Only people with the permissions announcer.receiver will receive announcements, but everybody owns the permissions per default.