Sync Firefox and Chrome passwords?

Use a plugin like LastPass that works with multiple browsers (including Firefox and Chrome). It will take over the responsibility of storing your passwords (potentially more securely than the browsers do natively). And it will auto-sync between systems and browsers without any additional configuration on your part.

I recommend using Firefox built-in sync feature which is?

but if you are determined to use Chrome (applicable in version 16).

1. Chrome (Wrench) -> Settings

2. Users -> Import Bookmarks and Settings -> select Firefox

3. Select items to import has a Saved passwords checkbox

You could also use a portable install of KeePass in Dropbox to have all your passwords available from anywhere.