You can buy a washer/dryer combo that is ventless. I have heard these models don't dry as well though.
I went through the basement and through the underbelly. Then I used a standard vent that can be bought at Home Depot. Here's a rough picture of the duct work through the floor (behind cabinet access panel)
Here's a picture of the vent.
-R.Jones
Nitro 31FQSL