FireFox Mozilla Useful Plugin

Firefly - A filemanager in your browser.
mozImage –Allow you to browse images on your local disk and on a web page.
FireFTP - a free, secure, cross-platform FTP client for Mozilla Firefox which provides easy and intuitive access to FTP servers.
Simple Mail - Mail client (POP3/IMAP/SMTP) for Firefox.
Firefox Universal Uploader –As the name says, this firefox extension allows you to upload/download files from any website using a friendly interface. Upload files/photos/videos to Flickr, Picasa, Youtube, Box.net(1GB of free space), Facebook, Webshots, OmniDrive, SME Storage and Google Docs in this version. Next versions would support other websites like Google Videos etc. You can add multiple files to the queue at a time.
Gspace - This extension allows you to use your Gmail Space (4.1 GB and growing) for file storage. It acts as an online drive, so you can upload files from your hard drive and access them from every Internet capable system.
Better Gmail - Add useful extra features and skins to Gmail, like hierarchical labels, macros, file attachment icons, and more.
Google Tool Bar -讓 Google 的強大功能伴您遨遊網上世界。
Google 筆記本擴充套件 - Google Notebook