By default you can't see your Library folder in Finder in Mac OS X 10.7, also known as Lion. Fortunately there are several ways to access it sill. My favourite is this one:
Holding down the Option key will show the “Library” directory as an option in the Finders Go menu. The other nice thing about the Go menu is that after you have accessed ~/Library on multiple occasions, it will start to appear in the “Recent Folders” submenu for easy repeat access.