I'm looking for an addon that tells me to turn off Aspect of the Viper when my mana is full. I've tried stuff like ViperWatch and ViperNotify, but they all seem to be broken since 3.3, and I can't find any working replacements. Any suggestions?
AutoAspect. You're welcome. :)
Another way you could do it is to use Power Auras Classic, and set up 2 auras. 1 to detect your mana level, and another to track what aspect you're in. This would be rather complicated though, and I'd advise using an addon like the one Jorn86 linked above unless you've used it before.
Power Auras is a very powerful tool though.
I use ViperNotify, you're able to configure it to show a message on your screen when you're at full mana (you can set the percentage it will do that if you don't want to go to 100%) and make noises and such.
Allow me to shamelessly plug AnnoyingBuffReminder, which will remind you to use an aura other than Viper when you have more than 90% of your mana. It will also remind you if you have no aspect on, and will optionally remind you to make sure Trueshot Aura is up.