As quoted from the frum (ultraorthodox) blogger below, Judaism presents an irresoluble contradiction about sex. On the one hand, the man avoids shaking hands with a female and even to look at her, but on the other hand, the Halacha (Jewish Law and Comments) is wildly liberal about what may happen between man and wife. In fact, everything goes.
Judaism allows, no!, advises, no! invites variety and experimentation. I know, one Rabbi, Johanan ben Dahabai, says that it is forbidden to "overturn the table" (practice unnatural intercourse or unusual sexual positions). But the rest of the Rabbis explicitly disagree with him: "A man may do whatever he pleases with his wife. A woman once came before Rabbi and said, "Rabbi, I set a table before my husband and he overturned it." Rabbi replied, "My daughter, the Torah has permitted you to him. What can I do for you?" (Nedarim 20b)
Our sages have also weighted the issue of unnatural sex (biyah lo kedarkah), such as oral sex, anal sex, or what the rabbis termed "threshing within and without" (premature withdrawal). Talmudic sources permit it with the proviso of avoiding wasteful spilling of seed, which Judaism abhors. However, it is not considered like the act of Er and Onan unless there is intention to destroy the seed and it is a habit to always do so. If it is occasional and it the man's desire to come upon his wife in an unnatural way, it is permitted. (Tosefot on Yevamoth 34).