Once I start I'll want to quote them all.
This site has pulled together 500+ first lines of novels, which you can browse at your leisure, and vote for.
Some of my favourites are Slaughterhouse 5 (Billy Pilgrim Came Unstuck in Time) , Snowcrash, Neuromancer. I also like the beginning of classical children's novels: Alice in Wonderland, Wind in the Willows, Samuel Whiskers:
Once upon a time there was an old cat, called Mrs. Tabitha Twitchit, who was an anxious parent. She used to lose her kittens continually, and whenever they were lost they were always in mischief!
On baking day she determined to shut them up in a cupboard.
She caught Moppet and Mittens, but she could not find Tom.
On a slightly less edifying note, this site has pulled together references to big dicks from a range of classical and modern literature. Well, it saves time doesn't it? It even has a section on Shakespeare.
Mercutio: Why, is not this better now than groaning for love? Now art thou sociable, now art thou Romeo; now art thou what thou art, by art as well as by nature. For this drivelling love is like a great natural that runs lolling up and down to hide his bauble in a hole.
Ben: Stop there, stop there!
Mercutio: Thou desirest me to stop in my tale against the hair.
Ben: Thou wouldst else have made thy tale large.
Mercutio: O, thou art deceiv'd! I would have made it short; for I was come to the whole depth of my tale, and meant indeed to occupy the argument no longer.
Romeo Here's goodly gear!