With the release of Mac OS X Lion, Apple made the decision to hide the user Library folder. This decision was based on their need to protect the user from accidentally deleting important files needed by various programs as well as the operating system itself. It became even more necessary for most users with the widespread use of the OS X App Store. However, I have found that some users still need access to this directory from the Finder, and am pleased to post the following fix. This is taken from the TUAW article cited at the bottom.
However, there are others that would prefer to have this folder reappear more universally. This involves using a Terminal command window (Applications->Utilities->Terminal.app). All you need to do is to paste the following into the Terminal window, change the text for [username] to your username directory (of course) and hit enter. That should do it!
chflags nohidden /Users/[username]/Library/