Can ice blocks placed in the nether be used to produce water?
It used to be possible to get water into the Nether with this, but as of Minecraft 1.3.1, ice blocks in the Nether simply disappear when they're broken (or when they melt from a light source).
Ice blocks can now be legitimately obtained in survival mode by harvesting them with a Silk Touch enchanted pickaxe. However, the ability for ice to create water in the Nether was removed.
So no, you cannot get water into the Nether using ice blocks.