(Click on the image to go to the page).
Why not get creative and use the Desmos graphing calculator to produce some Christmas art work? As you can see the tree above, featured in the Desmos Staff Pics: Creative Art is simply a collection of line segments and circles. You can see from the syntax that it is very easy to restrict the values for x (or y). For any students unfamiliar with the equation of a circle you will see that (x-a)2+(y-b)2=r2 is a circle, radius r, centre (a,b). To experiment with circles, try this page or click on the image.
If you are counting the days till Christmas WolframAlpha will of course help you or use an Nrich advent calendar, two are available one for primary and one for secondary school students. These provide activities for each day in December. For another advent calendar see the Plus Magazine (always an excellent read) 2012 advent calendar.
Wishing you all a good end of term and a Happy Christmas.