By default, the ~/Library folder is hidden in Lion. This is a big problem to many of the readers of this site, as many hints involve this folder (especially any involving hidden preferences).
You can easily un-hide this folder for easy access. Simply run the following command in Terminal:
chflags nohidden ~/Library
If, for some reason, you want to re-hide it, you can run the same command using 'hidden' instead of 'nohidden'.
You can actually use this command to hide or unhide any folder. Just put it's path in place of ~/Library.
[crarko adds: Works great. One of the first things I did.]
Mac OS X Hints