The Gmail offline utility is cool. It uses Gears on your computer to store your latest mails.
It is much better than the email clients like Outlook or Evolution as it organises your mails in the same way as Gmail does using the uber-cool AJAX. The mails are stacked together in a thread for ongoing email correspondence.
Now, Gmail also loads more quickly than before. WordPress also uses Turbo (that uses Gears) to store files (of your blog) on your computer to speed it up.
However, it is to be used ONLY on your personal computer-it doesn’t require password.