I might as well make a whole card strategy out of this versatile card, that reads:
Card Name: Traumatize
Mana Cost: 3UU
Type & Class: Sorcery

Card Text: Target player puts the top half of his
or her library, rounded down, into his or her graveyard.
Now, in addition to the aforementioned and largely obvious traumatize/haunting echoes combo, Traumatize will work great with other cards as well.
First cards I can think of off the top of my head are the new (and I guess the original) Lhurgoyfs.  Half one's library, let's say 20 cards, can add greatly to the power and toughness of those guys, with variation, of course.  I would say on average, it'd maybe get them, I dunno, a +4 or +5, depending on the type of lhurgoyf and the type of deck you're playing.  But hey, it still looks pretty damn neato.
Secondly, you can Traumatize yourself, and combine it with a Nefarious Lich to net yourself a good amount of life.  Granted, you lost half your library, but it could have saved the game for you, so the tradeoff, in my mind, is worth it.
Another set of cards you can use with Traumatize is Bearscape, and its Fallen Empires predecessor, Night Soil.  Bearscape is a new Odyssey card, that gives you a 2/2 bear for removing 2 cards from your graveyard (meaning you have to Traumatize yourself, I know).  Night Soil lets you remove 2 CREATURES from ANY graveyard.  So while it is more restricted in type, you don't have to traumatize yourself.  Night Soil is great if you play a saproling deck, and especially if you have one of those all important Coat of Arms out, or even an Elvish Farmer for a load of life.  And don't forget the Overrun.
However, the last card I want to share Traumatize with is...*drum roll* Living Death.  Yes, we all know how powerful Living Death is...but...Look at it if you traumatize yourself!  Granted, you'd lose any creature out in play, but who cares?  Load your deck up with Spirit of the Night's, Tidal Kraken's, and any other big fattie that you probably could never get out normally without outside help.  Your opponent would also get his creatures back, but hell, Living Death is black, so load up your deck with Cremates or the new card Gravestorm.  To be honest, you can even use (probably should use) Buried Alive, since they did reprint it and all.  So, in conclusion, get all your big fatties (Mahamoti, Tidal Kraken, Desolation Angel, Spirit of the Night, whatever your heart desires) in the graveyard using Traumatize or Buried Alive, and then spring them all into play with Living Death. 
On another note, why doesn't the Childhood Horror Traumatize you?