Rainlendar is a customizable calendar that displays the current month. It is a very lightweight application that doesn't use much system resources or take much space on your desktop.
Small and lightweight
Different type events can have different appearence
Supports Windows transparency
Synchronizes events between several clients
Localized for multiple languages
Shows an alarm when an event is due
Supports iCal files.
Shows Outlook's appointments
Includes a todo-list