This is a long weekend in the U.S., at least for the staff at the U. Hawaii.
I knew I had to work hard this weekend, because I agreed to give a seminar on Thursday and I need a lot of test experiments to decide on our main run (control run) for my talk and for our paper. I went to work for an hour or two each morning, to exam the finished test runs and to design some new ones. When I need to pick on someone's brain, I call one of my collaborators. (So, I am not the only scientist who works on weekends.) On Sunday evening, I decided to go to work briefly, in order to speed up the progress (since each numerical test takes 10-12 hrs of wall clock time). I may go to work again this evening, depending on how I feel.
Of course, research is not the only thing I do on weekends. I shop, I cook, and I do a bit of cleaning at home. I also email, Blog, and watch movies. However, my mind is never too far away from my research, no matter what I do. (Yes, I do dream about my research some time.)