Dota Mana Bars - A Warcraft 3 tool that allows you to see mana bars along with health bars. You may use this tool in LAN games and it will work out fine. It really helps when you're Anti-Mage or Nerubian Assassin. However, many people reported that this causes Warcraft to crash when playing on Garena and B.Net and many tournaments might ban use of this tool as it provides you with an advantage over the enemy. So I wouldn't suggest using this on Garena and B.Net at the moment. It's worth trying on LAN anyways.
ManaBars 1.4 download link:
After extracting the files from the zip folder, run the program and Warcraft III in whatever order. :)
Note: If you disable "Show HP Bars" option in Warcraft 3, the manabars will also disable.
Hope Blizzard implements this tool in warcraft next patch.