MTG: Enchants?

Question

Is it possible for enchants like Oblivion Ring to be casted on other permanents instead of on the enemy permanent you want to destroy? If so, can it also be cast on lands and artifacts ?

Answer 1

First off, Oblivion Ring isn't an aura.  So it really can't enchant anything.  Secondly, the ring will remove anything other than lands from the game, including itself.  Here are the official rules for O-Ring.

10/1/2007 If Oblivion Ring leaves play before its first ability has resolved, its second ability will trigger and do nothing. Then its first ability will resolve and remove the targeted nonland permanent from the game forever.

10/1/2007 If there are no nonland permanents in play other than an Oblivion Ring, and the card it removed from the game was another Oblivion Ring, playing a third Oblivion Ring will result in an involuntary infinite loop that will end the game in a draw (unless someone chooses to break it by putting another nonland permanent into play or destroying one of the Oblivion Rings, for example).

Answer 2

First off, Oblivion Ring states it can only target a non-land permanent.

Unless a card states it can only target an opponents permanents, it can target any legal target in play.  You can cast Oblivion Ring targeting any non-land permanent in play including your own.

And yes, that includes artifacts (unless it's an artifact land)