Can prepositions be used to end sentences with?

Sure. Questions, too! It's a good idea, though, to try and make your point, or ask questions (I liked this one, though), without a preposition as caboose, whenever possible. Here's what the author of The Grammar and Style Guide and A Reason for Living, Laurent Grenier, wrote on the subject:

"Many grammar experts in the past insisted that a sentence should never end with a preposition. In most cases, the rule still holds. Nearly all experts now agree, however, that a preposition may appear at the end of a sentence if moving it to another position would create an awkward construction.

Weird: I want an income on which I can count.
Better: I want an income I can count on."

More from the same author: "Sentences can end with prepositions, despite the oft-heard dogma that they should not, but a sentence that does is likely to be a sentence in which the word order is not standard, because in standard word order a preposition is followed by its object."

Listen to how funky, "What are we waiting for?" sounds when it's grammatically correct: "For what are we waiting?" At least I think that's correct, LOL. It's hard to imagine saying that, even if it is "correct." I'm not sure if every rule was made to be broken, but I can think of one or two that shouldn't be used without considering the situation.

Sometimes all that's needed is a small preposition-ectomy. Remove, and listen to the result. You might be surprised. I wrote an answer that ended with "..or anything else you already know about." in the dreams category. It sounded right, but clunky, so I tried rephrasing and rearranging, including "...anything else about which you already know." I finally realized "about" was unnecessary - and ended up with
the stronger, more direct, "..or anything else you already know."

Hope this is helpful.

http://www.laurentgrenier.com/grammar&style.html

You never end a sentence with a preposition. why? its bad grammer and it makes one sound like a red neck. example: wheres my comb at?
pure red neck.

People judge you by the english you use. ending a sentenc, with a preposition....IS DEFINITELY NOT WHERE IT IS AT ! see what i mean?

Many of the silly rules of English grammar come from the even sillier idea that English grammar should be the same as Latin grammar. (All grammarians in merrie olde England studied Latin grammar.) Latin sentences can't possibly end with a preposition, or split an infinitive, so they applied the rule to English. But there is no more reason to apply Latin grammar to English than there is to apply Hebrew, Chinese, or Sanskrit grammar to English.

Here's a joke about that stupid rule.

This kid's father was an English teacher who'd worked a year in Australia, and he was a real bore on both subjects. When the kid ended a sentence with a preposition, he had to go up to bed early, but his father promised to read him a bedtime story. "But not about Australia!" the kid said. Well, his father brought up a book about the Great Outback (desert). The kid looked at the book and said "What did you bring that book that I didn't want to be read to out of about out back in Down Under up for?" (Sentence ends with 11 prepositions.)

I"ll check to see if it is correct by consulting my copy of Fowler's Modern English Usage, if only I could remember where I left it at. But first, tell me what you need this information for. And whom are you going to share this information with?

It's not proper and not needed. Just like your question, you shouldn't have ended it with with. There are exceptions.

http://grammar.quickanddirtytips.com/ending-prepositions.aspx

Now, where's the next question at?

Well, you just managed it. According to tradition we shouldn't - but most of us do.

As another has pointed out, there was a period in Britain where the lofty ideal was to have English mirror the classical languages as closely as possible. (This, however, borders on the impossible.) The three best-remembered cases of this misplaced zeal were the "horrors" of split infinitives, multiple negatives & a preposition at the end of a sentence. All three usages have a very long history in English. Those "ideals" were primarily promulgated by a group one of my professors described as "retired theologians and amateur philosophers." Whenever the speaker's / writer's meaning is clearly conveyed, none of those three usages presents a problem except for nit-pickers and hair-splitters who have divorced their thinking from the realities of a living language.

why not ? the answer lies in the question itself. If you are not confused with the prepositions or questions, you can use conveniently.

Eg: what are you looking at / for?
who are you talking to / with ?
What are you listening to ?