This isn't really a hack - but if you really want to do home desalination then there are some practical solutions.
Ocean-going boats have desalination pumps for providing their fresh water. They refer to them as a "watermaker". A quick look on ebay yielded one for c.3000USD.
There's a hand-operated version that they put in life-raft. Not cheap:
http://www.nitro-pak.com/katadyn-survivor-06-desalination-watermaker
...but again on ebay for about 100USD.
There a thing called a "solar distiller" that I think they also use in liferaft. Can't find a price at the moment but they are very basic so should be dirt-cheap.
EDIT:
The only way to save on the huge energy requirements of desalination is to use solar power.
Aside from the small inflatable solar distillers that I mention above, I also remember seeing a very hacky thing done on TV many years ago. The guy dug a pit in the ground about 20cm deep and lined it with black plastic. He the erected what I can only describe as a "tent" of clear plastic over the pit but in such an arrangement that a plastic gutter ran along the bottom edge of the sloping sides into a collector. The water evaporates due to energy absorbed by the black liner and leaves ALL contaminants in the pit. It condenses on the slopes and runs into the gutters and thence into your collector. Voila - fresh drinking water from any contaminated source you can find - for free.
The downside is that you have to regularly flush-out the bottom of the pit. I'm sure a bit of ingenuity could eliminate that step by making it automatically flush itself on a regular basis. For example, I've envisaged a long, shallow sloping bed with a poly-tunnel roof over. Dirty water continually trickles in at the top and evaporates, the residual water continues down the slope and out to waste.