Depending on who your homeowners' coverage is with, a computerized sewing machine can be considered "electronics". Most policies have a built-in limit for electronics, over and above the contents limits. That limit usually isn't much, and this is where even the LED/LCD tv's and computers would be covered too. So if you have a lot of "electronics", my agt suggested covering these, including my 3 machines, on a rider that increases the electronics limit.
I take pictures of everything and store them away from the house. Copy it all on CD. If you have something really spendy, like sewing machines or longarms, making a copy of the receipts and storing it too is a good idea. Serial number documentation too.