HOI !

No, not the dutch version. The japanese.
It's like when you see your mother sporting a huge black strap-on, getting ready to join in on your girlfriend and you, you'll shout out "HOI!" because... ...what?
Is it some kind of exclamation of lustful desire? What's the closest translation?

...and while we're at it, "iyaaan", that's some kind of a blushful expression, right? ...and "Moooe?" is some kind of expression of cluelessness?

So last night I was having sex with this girl and she kept screaming "yamete". That means "moar", right?

Heh, well that means "stop", but you'll have to understand that japanese women ALWAYS say no to sex. She actually wanted it.

Well, I don't know about ``HOI,'' whatever you mean by that (a sample would be useful).  I can however tell you about ``iyaan'' and ``moee.''

Iya~n, is a thing girls say when they are pretending that they are embarrassed (although they might be as well).  It's probably derived from ``iie'' which means NO which is what iyan is usually translated to.

Moe~, I assume either means that something is Moe [1], or that the person saying it is on fire (figuratively speaking).  These meanings are pretty much only used by males though, so if you are thinking of something else, please provide a sample ;)

[1] http://en.wikipedia.org/wiki/Moe_%28slang%29

I'm translating the forbidden text of "Sister pudding-pudding"(?), and there are passages containing both "Hoi!", "Iyaan", and "Moo" (もぉーーっ!). (Not "moe" - sorry.)
Hoi-and-iyaan-context (where a brother and sister is having sex):

"お兄ちゃん許してね (いやぁん)
O-nii-cha-n ?-shi-te-ne (i-ya-a-n)

ほいっ！
Hoi!"

Also, I'd like to know what the "~" sign is for. It doesn't say anywhere on the net how it's used. It only tells us about the "-" sign.

もぉーーっ!
This could be either the sound a cow makes, or the word "mou," for "enough".

ー
This basically means you extend the last sound ;)

ほいっ！
Considering there is an exclamation mark after it, I assume this is the "oi"-expression -- which can be translated to ... hmmm, "whoa," I'd say ;)

>>7
tilde~

>>9
It has already been explained to me in another thread: It's an elongation with a wavering, as opposed to an unwavering elongation. However, it can also be used as a marker for "to/from", like "monday ~ friday", I've heard.