Tricks to make most people leave:

"I'm really tired." "It's getting late." And such statements.
Work in the morning? Early appointment? Breakfast plans with another friend or family member? Church? Discuss!
Your favorite TV show is on and just happens to be on PBS- BORING!
Husband, child, room mate? Need you quiet by said time and you'll abide.
Just go to bed! Be careful of the friend who might want to come too! Unless you're up for that...
Are they bussing? Offer bus times or to call a cab!
Suggest going out then, leave on your own terms.

And my favorite: "GTFO!"

Oh and over feeding might work, if they're too embarassed to poop in your bathroom!