Spiffy is an advanced Gmail notifier for Windows, it's free and completely customizable.

Changelog:
added portuguese translation (Thanks Mario)
added option to set custom browser
added option to always hide main window
added option to show unread count for all accounts in tray
added GIF and JPG image types for custom alerts
added option to log errors to file
added alert sound test button
added 'working' icon in main window when checking for new mail
tell me again now shows all missed alerts
accounts and configuration windows now accessible from tray
fixed height setting of alert textfields (default to 14)
optmized localization code and removed unused resources
updated accounts and configuration windows

Program Information Category: Tools and Utilities Type: Free Version: 0.5.5 Size: 278KB Works on: Windows Product page: here