Hallo,
I often use Firefox, a great browser, and sometimes go to Tools - Options - Security - saved password to read and erase the passwords for the sites that I visit.
Do you know if there is a way to shorten this path, maybe insert something in the toolbar to speed up this task?
Thank you

No, I don't think there is. I know it's convenient, but it really isn't secure letting any web browser remember passwords.
The best way to save to doing what you currently do is to set Firefox so it doesn't remember them.

In Firefox 3.5 you can go to Tools > Clear Recent History > Select only password and clear. Next time you will only have to click it. There are also plenty of Firefox add-ons that can clear your privacy in one click. Do a little search on Firefox add-ons site.

An easy shortcut in Firefox to clear your private data is CTRL-Shift-Delete. Try it.

Another recommendation I have, if you are using Firefox to store your passwords, consider setting a Master Password (it's in the option screen too). This way as soon as you load Firefox, it will popup and prompt you for your master password. If you get this password wrong (or click cancel - for someone else using your computer), it will not auto-fill any passwords you have saved. It uses this single master password to encrypt all your other saved passwords.