Oh, there are soooo many. I hardly use proper English at all.
Online dictionaries will often give you only the swear words, which of course are good to know, but generally are not nearly as interesting as the really creative stuff.
Here are some American slang expressions.
Oh, for crying in the mud. (A variation of "for crying out loud.")
For corn's sake. (both bemused exclamations, said with a Minnesotan accent)
Son of a buckeye! (instead of son of a b*tch -- a rude exclamation)
Peace out, girl scout. (a farewell)
What up? (a greeting)
Dude (all purpose greeting, farewell, exclamation, question)
Kelly Clarkson! (exclamation said while in pain)
snooze (to sleep)
my peeps (my friends or family, my people)
rug rats, ankle biters, carpet monkeys (small children)
pooch (a dog)
dog (an ugly person or a low performing stock or company)
dirtbag, sleazoid, scumbag (a person of low character)
rockin' out (really enjoying music, often including singing and/or playing air guitar, and sometimes in a car at a traffic light)
chill out (relax)
SMIH (see me in hell. Something you say to or about someone who really annoys you, as in "The American news media can see me in hell." When writing, "I am having such a bad day at work. I'm about to tell my boss she can SMIH.")
-aholic (suffix that can be added to almost anything, as in chocoholic, workaholic, sexaholic, shopaholic. From the word "alcoholic," because isn't that just a fantastic thing to base your language around?)
OK, it's 4 a.m. here. That's the extent of my brain power. Good luck!