Ben Witherington has a pretty good post talking about the biblical teaching on hell. Here is part:
What I am more sure of than ever, is that there is no salvation outside of Jesus Christ, and that in the end ‘every knee will bow and ever knee confess’ even those humans or demons who want to have nothing to do with Jesus thereafter. Salvation in the end is not just a matter of being forced to recognize the truth— it’s about positively embracing and trusting that truth. And there are apparently some who will never ever do that. To them God says “if you insist, have it your way”. Hell is the place you experience the absence of the presence of God for as long as you continue to exist. Whether there is a time when Hell will cease to exist, like the crystal sea of Revelation, equally orthodox persons can debate. Anihilation or destruction of Satan, Hell and its inhabitants is a possible interpretation of the eschatological endgame, but it is also possible Hell will go on ‘olam wu olam wu olam’. If the former is true, then the last persons standing are all followers of Christ according to Revelation. Rev. 21.8 seems pretty clear— “But as for the cowardly, the faithless…etc. their place will be in the lake that burns with fire and sulphur, which is the second death. Even more telling is the statement in Rev. 22.15 which states that after the new heaven has landed on the new earth and the new Jerusalem has been set up, “outside are the dogs and sorcerers and fornicators and murderers and idolaters, and everyone who loves and practices falsehood.” It would appear from these last two text, that Hell still has a future, even after the new heaven and new earth show up at a theater near you. What this suggests is that love, even divine love, does not always win with everyone, not even in the end, and it breaks the heart of God as it should break ours.