My house has pretty much always looked like that. Sometimes better, sometimes worse, but always messy. I've made a great deal of progress in the last couple of years by getting help, making an effort, really thinking about where things go, and decluttering. Some suggestions:
1) Get help. Hire someone, pay your kids to do one room, bribe your friends with pizza and beer. Just clearing enough stuff away to allow people in your house can be a big step and a big motivator. Do something!
2) Throw crap away! Get rid of junk! This will help A LOT. Don't hold on to crap you don't need. Identify stuff you need and then taking it all the way out the door to the trash or Salvation Army.
3) Do one thing at a time: one room, one corner. Clear a path! Progress not perfection.
Here are some resources I highly recommend:
flylady.net. This is a good one, because they have a daily task, and baby steps. A little cutsie, but still good.
http://www.flylady.net/