Available Modifications
Listed below are modifications that advanced users may chose to impliment into the rendering of overviewer. These mods may include additional information overlays into the output, the style in which tiles are rendered, or additional actions that are performed by overviewer on each run. These typically require the administrator to have a little more knowledge of programming languages... as a note to developers of these mods, please feel free to update this list with links to your own scripts and mods.
PlayerMarkers https://github.com/overviewer/Minecraft-Overviewer-Addons/tree/master/PlayerMarkers - A bukkit plugin and overviewer javascript file to show ingame player positions live on the rendered Overviewer map. Multiworld Compatable and supports either MapMarkers or PlayerMarkers bukkit plugins.
Player Avatars https://github.com/ethzero/Minecraft-Overviewer-Addons/tree/master/Player-Avatar - PlayerMarkers originally used this php script, if you would like to host your own copy instead of relying on the centralized player avatars script hosted at overveiewer.org, then you'll need this script (or one like it).
Millenaire Support In Overviewer http://minecraft.tournier.org/ - A tool that can generate a new Minecraft Overviewer textures jar including Millénaire's textures, and modify installed Overviewer software taking into account local block IDs, so that the Minecraft Overviewer can support Millénaire's buildings rendering. One example here (the markers are generated by the following tool) and a comparison before/after there. Made for Overviewer 0.11
Make My Overviewer POIs http://minecraft.tournier.org/ - A utility to generate Minecraft Overviewer markers and information popups from your Minecraft world, showing villages, and optionnaly jungle/desert temples, witch huts and strongholds portal rooms (!), with an option to have custom labels. If the Millénaire mod is installed, it will also generate a marker for each village and lone building, with a flag colour showing their respective culture, a label giving their name, and a popup with detailed information (in English or French) about the village culture, type, population, the number of buildings, the village relationship with other villages, the players reputation. One example here. Made for Overviewer 0.11
(may not work with Overviewer 0.9+)
Minecraft Sundial https://github.com/sunkid/minecraft-sundial/ - Will show your ingame server time as an overlay onto the Overviewer Map.
WorldGuard2OverviewerRegion https://github.com/overviewer/Minecraft-Overviewer-Addons/tree/master/WG2OvR - This php script takes the regions defined in WorldGuard, and outputs them in isometric cubes on your overviewer map.
MCWeather https://github.com/overviewer/Minecraft-Overviewer-Addons/tree/master/mcweather - Add a current weather and forecast icon to your Overviewer map.
Menus http://code.google.com/p/overviewer-menus/ - Allows other addon developers to create simple menus.
WarpMarkers http://dev.bukkit.org/server-mods/warpmarkers/ https://github.com/deadcyclo/WarpMarkers - Shows /warp-points from Essentials on the map. Includes created by, time, last used by and time. Also shows /warp-points alerts (created, deleted, used).
Online Players Add a list of clickable links that displays players online. Updated for build June20th build.
Base code by pironic & ethzero of github, I simply updated it and moved the styling to the overviewer.css
https://github.com/KariTrace/Overviewer-Players-Online-Update
Re-Packaged Overviewer (with Add-ons) https://github.com/FabianN/Minecraft-Overviewer - This is a fork of overviewer with add-ons included. Comes with MapMarkers, Player Avatars, Sundial, WG2OvR, and mcweather. All you need to do is point WG2OvR, mcweather, and Sundial to the location of your regions.yml and level.dat files (details are in the README).