Added GMail Features

GMail Helper
The Gmail Notifier by Google is a downloadable Windows application that alerts you when you have new Gmail messages. It displays an icon in your system tray to let you know if you have unread Gmail messages, and shows you their subjects, senders and snippets, all without your having to open a web browser.

GMail ToDo NEW!
Keep a ToDo list using your GMail account!

GMailFS NEW!
GMail Drive is a Shell Namespace Extension that creates a virtual file system around your Google GMail account, allowing you to use GMail as a storage medium.

gPopper NEW!
Acts as pop3 Gmail server allowing you to use programs such as Outlook and Outlook Express to send and receive Gmail.

GMail File System NEW!
Maps itself as a Gmail drive in Windows.

Pop Goes the GMail
Lets you access your GMail account with a POP3 mail client.

eMail2Pop
Interfaces with Gmail to provide POP3 and SMTP access to Gmail accounts.

GSuite
A simple, unified interface with all the tools to enhance your Gmail experience. Providing quick access to your account, easy search access, new mail notification, 'mailto:' handling and much more..

GNotify
Gmail utility that runs in your systray and notifies you when you have new Gmail.

GmailerXP
This program, still in development, will offer total control of your GMail account from any Windows computer.

GTray
Lives in your system tray and alerts you to pending GMails.

You've Got Gmail
Trillian plugin that adds the ability to manage and monitor multiple GMail accounts.

GCount
Lives on your Mac and alerts you to pending GMails.

OSX GmailStatus
Alerts OSX users to unread mail, makes access to GMail easier, and even lets GMail act as your default mail client.

GMail Notifier 
For FireFox/Mozilla, adds an icon to your toolbar that keeps you updated on the number of GMails you have waiting.

G-Mailto
Rewrites any mailto link on a web page so that it sends using your GMail account and not your local mail client. 

G-Mailto for Mac
Same as above, but works on computers with pretty apples on them. 

GMail Compose
Adds a context menu to Firefox that lets you right click a mailto link and compose a new GMail..

G-Mailto Bookmarklet
Launch a new GMail with a bookmark!

Using GMail For Backup
PHP script that can be used to backup files to Gmail and then quickly retrieve them back if and when you need them.

gmcp: More GMail as Backup
Yet another way to use your GMail account for file storage.

Mail Upload

GetMail
Auto-Forwards Hotmail messages to GMail.

YoSucker
Makes it possible to access your Yahoo! Mail using a POP3 client.  Some have successfully used this application to download their Yahoo! Mail and then re-upload it with GML.

Tim Commer's OSX Applescript
Makes using GML .4 much easier on OSX. 

gExodus
This application was designed to include some of the original features of GML but include a GUI.  It only includes support for mBox files.  I have since added a graphical interface to GML, and support more message store types, but this utility may be of use if GML doesn't work for you.

Mailbox Conversion

AddressBook to CSV 1.1
Converts OSX AddressBook format to CSV for GMail import.

PST Reader
Can convert PST files (from Microsoft Outlook) into mBox format.

juno5bdb
Extract Juno 5.0 email folders and messages to mBox.

Trevor Harmon's mBox Cleaner
Fixes pesky mBox files created in Mozilla or Thunderbird, and good for double checking others as well. Included are both the source and the compiled version.

ReadPST
This application may be able to directly convert your Outlook PST files into mBox files GML can use. It's a command line utility, execute readpst.exe for instructions.

Outport
Exports data from Outlook to some useful formats for upload to GMail, and other uses.

DBXConv
Can convert DBX files (from Microsoft Outlook Express) into mBox format.

Programming Related

MINCUS - Mail::Webmail::Gmail
Mail::Webmai::GMail lets you access GMail through a Perl module.

libgmail
A project to allow Python applications access to the Gmail service. Included are demonstration utilities to archive mail to mbox format, allow sending by standard mail clients via a SMTP proxy and selected download of mail attachments using a standard FTP client via a FTP proxy.

gmail-lite
A PHP library/class that helps you accessing/checking/using GMail through PHP scripts.

Mail Notifier & Address Importer
An open source .NET GMail API and a windows utility that provides notification and address book import.