They are not the same thing. Sausages are any kind of meat (or animal product) and spices in a casing. Weenies or wieners are a specific TYPE of sausage. They have a smooth texture, meaning that when cooked the outside skin is smooth rather than rough, and are typically made from a mixture of beef and pork. Wieners, hot dogs, and frankfurters are the same thing. Italian or breakfast sausage will have a rough texture when cooked, and are not called wieners. Other smooth-skinned sausages, such as liverwurst or blood sausages, are made from ingredients and spices that are different from wieners. The slang meanings mentioned by the other posters are correct.

Weenies! Weenie is slang for Wiener. Hey, y'all are invited to a weenie roast at Hanny's place! 'wiener' is also children's slang for penis (for obvious resemblance) and it is also slang for someone who is annoying. I suppose it's like an immature 'dick' (jerk) "Billy, cut it out! Stop being such a wiener!" A related slang is "Weenie" for someone who is a coward or whines. "Joe's little brother wouldn't go on the rollercoaster. What a weenie." And then there's a (rather corny) english expression which is a variation on 'That's a winner!': "That's a wiener!" And finally, dachsunds are also known as Wiener dogs, because of their short legs and sausage-shaped bodies. A town near me lays claim to the title of 'wiener dog capitol of the US'. I don't know why they like them so much, but every year they have a wiener dog parade. Gary Larson used to make wiener dog jokes somewhat often in his cartoon "The Far Side"

it's spelled as wiener pretty much the same thing, sausage, wiener or hotdog winnie is a girl's name :)

duquup is right. weenies might be an american slang, where we have low taste and little experience with exotic wurst. Hot dogs are not quite the only sausage in america, but they outnumber the others 10 to 1.

"wienie" actually. sausages and wienies are quite the same - as main ingredient is pork or beef, but different in taste. wienie are usually "smoked".