If you’ve upgraded to Lion and can’t find your personal Library folder anymore, don’t worry; it didn’t disappear. It just doesn’t show up in Finder because Apple decided to hide it by default. They probably did it to save certain users from themselves, but for those who are interested, all you need to do is run one command in a Terminal to easily see it again:
chflags nohidden ~/Library
Now you can go back to messing with your Applications.
It appears that you must do this with each update. My ~/Library was hidden again after updating to 10.7.1.