[pooriaazimi]

This is 100% off-topic, but since this submission has 100+ upvotes and many might view the comment thread, and you mentioned Library/ folder, I think it's good to point out that you can easily make Library/ folder visible again in Lion.

Just type:

    chflags nohidden ~/Library

in the Terminal.

[evilduck]

You can also access hidden directories from Finder with Cmd-Shift-G and manually typing their path.

Personally, I infrequently access my ~/Library and I know it's there and what it contains and I can hop over to it quickly if needed that I prefer it hidden for visual simplicity.