Springfield blogger Marie of Disarranging Mine fame tipped me off to this site. It's full of bar tricks, many of which use beer or beer bottles. Easybartricks.com has a couple of dozen tricks you can perform to amaze your drunk friends and your designated driver.
Note that you have to follow the links as the pictures below are just screen shots.
This one, called Freezing Beer, you will have to do at home rather than at the bar but is pretty cool nonetheless.
Actually, this next one would be best done at home in the basement if it has paint on the walls.
Here's a good way to win a bet at a bar using one finger only.
This one is more of a helpful tip than a trick. Occasionally, i find myself in need of a bottle opener but don't have one. There is always a way to get the bottle open but some are messy, some are painful and some leave a mark. This trick requires you only have a newspaper to open that beer and is without consequence.
There are lots of another tricks at easybartricks.com, so check it out.
Have a great weekend! And have a beer, that should do the trick.