I have just discovered that Shadowpriest.com is no more, while I wasn't a heavy user of the site, partly due to my infrequent use of the shadow spec, I did occasionally have use for it. 

It was during the Burning Crusade when I discovered the site and as I was raiding as a shadow priest for the greater part of that expansion, and I found the site invaluable as a way of increasing my DPS and knowing the BiS gear from the lists that were supplied. More recently, the help I received from the community (and a guild mate, Ronny, assisted but if I give Ronny too much credit I'll never hear the last of it) gave me a 20% increase in DPS, yes I was THAT bad. The official announcement taken from the US forums is below. 

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Power Auras was created to provide visual warnings when you gain very shorts buffs or debuffs, it allows you to draw in the centre of the screen around your character and is very customizable with many built in visual effects. Since its launch it has evolved and can now track

• Buffs/Debuffs (whatever their name)
• Debuff Types (like Magic, Curse, Poison, Disease, Silence, Stun, Crowd Control etc)
• Combo points
• Harmful area spells
• Weapon enchants
• Health
• Mana
• Rage, Runic Power or Energy thresholds
• Action cool-downs
• Aggro, PvP status
• Stance, Shape-shift form or Aura

TL; DR - its a personalised buff/debuff centre that can also help you track cooldowns to keep you alive amd maximise your DPS/TPS/HPS.

You can download it from:
Power Auras @ Curse.com
Power Auras @ WoWInterface.com

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