There is only one solution to Mana flooding in green: bigger, meaner creatures!
My recommendations in black depends a little on how many people you usually play in your local playgroup?

In Green I would suggest

• Hydra Broodmaster, since, if you have "too much" mana, you just make him into a 20/20, with 13 13/13 tokens to help him, and the game is pretty much over using only the small sum of 26 arbitrary mana and a .
  
• Feral Hydra, he's slower to build up than Broodmaster, but you can empty you manapool into him several times.
  
• Wurmcalling, because an X/X wurm every turn is going to really screw your opponents' day.
  
  

As I don't play Black ramp myself, I cannot talk from expierence in this, but I would recommend various 'pay x: kill your opponent(s)' cards, such as

• Exsanguinate kills multiple opponents, and fills your life with theirs (in case you can't kill all of them)
  
• Killing Wave board wipe, regardless of whether the creatures have protection, like indestructible.
  
• Profane Command this card has so many different uses: killing your opponent; returning a creature from the grave; killing/weakening a creature; or giving your creatures semi-unblockable (fear)
  
• Damnable Pact killing your opponent with either mill or loss of life