Aliza Hausman just posted a great video by Ma Nishtana about mythbusting that whole Jews have sex through a hole in the sheet thing. It’s kind of awesome.
Alternately, you can watch the Jew in the City’s answer, though I find it significantly less satisfying:
Or you can check out my own explanation, from my days at Jewcy.
Now that you know for sure that hole in the sheet are out, you may feel comfortable shelling out more money for really good sheets. Frette is having a sale, and some of their $900 sheets are marked down to less than $300. Or, you can just look for bamboo or otherwise organic sheets at department stores or in catalogues. I really like these organic flannel sheets from Gaiam (on sale for under $100). If you get them for me, I promise never to cut holes in them. Ever.