The Washing Machine is one of my oldest tricks, but it's still one of my favorites. I get a lot of requests for this one, however very few yo-yoers actually know how it's done.
The trick itself can look very intimidating but trust me, it's totally doable by any intermediate player.
The trick; a yo-yo starts attached to the string (like most yo-yos are) but is removed from the string and popped into the air before being re-attached... All while the yo-yo is still spinning.
I have attached a video demonstrating the trick, check it out.
The yo-yo; Any yo-yo can be used for this trick as long as it can sleep (spin at the end of the string). I've even used a Duncan Butterfly. As with any trick, the longer the yo-yo can sleep, the easier the trick becomes. So I suggest using any decent ball-bearing yo-yo. Using a butterfly shaped yo-yo would also totally be recommended.
It's a bit tricky for me to describe some of the moves in text, especially when a step requires you to switch planes (such as required popping the yo-yo off the string, or using your thumb to put it back in the loop). So if you have difficulty on a step (or a suggestion for a description change) please let me know.
For more yo-yo info and videos you can check out www.DoctorPopular.com. Thanks Phil and Shan for helping out with the pics.