OS X Lion hides the ~/Library folder from view in an effort to prevent users from tampering with sensitive files or unwittingly tossing out their precious data.
However, if you need to dig in there, it’s easy to get to your user’s Library folder with a simple Go > Go to Folder command in Finder, then typing ~/Library.

Moapp also found a Terminal command that can bring your library folder back into focus.

Open the Terminal and type:

chflags nohidden /Users/[username]/Library/

Alternatively, reader PBenz pointed out that you can hold the Option key when clicking Finder’s Go menu to make a hidden Library option appear, as pictured.

And thanks to Paul Conigliaro, you can also assign a shortcut in System Preferences > Keyboard > Keyboard Shortcuts to open ~/Library. I used Command-Option-Shift-L.