The lineup is pretty good, but my pick of the festivals is Metalcamp 2006 festival, set to take place July 21-23 in Tolmin, Slovenia.
Just look at the lineup!
AMON AMARTH
ARCH ENEMY
CALIBAN
CATARACT
DEATHSTARS
DECAPITATED
DIMMU BORGIR
EDGUY
EVERGREY
EXCELSIS
GOREFEST
HEAVEN SHALL BURN
HYPOCRISY
JON OLIVA'S PAIN
KATAKLYSM
KREATOR
MAROON
MY DYING BRIDE
MYSTIC PROPHECY
NEVERMORE
ONE MAN ARMY AND THE UNDEAD QUARTET
OPETH
SCAFFOLD
SCAR SYMMETRY
SOILWORK
TESTAMENT
WINTERSUN
Hellfest in France is pretty damn good too!