The Guardian posts extracts from this year's Bad Sex Award. But I'm with this columnist who asks, where's the good sex in fiction? In the comments section, there are some suggestions.
Or just read the brilliant A. L. Kennedy on the subject here. A sample:
Literature within which people have sex is, in many ways, curiously like literature within which people grind coffee, lick wet tea bags, play the trombone, or visit cottages – it simply involves a humdrum physical activity which has to be accurately described with a sense of personality, psychology, voice, tone and plot.