XDeskCal is a pretty,fully customizable calendar features Todo-list,Appointments,Alarms,Holidays and displays its data on your desktop. It is a very lightweight application that doesn't use much system resources or take much space on your desktop.
Features :

YearPlanner is a brand new, stylish, feature rich calendar tool with a difference. It presents calendar data in the 12 month wall-chart layout.

Plan events on a single multi-month page from 1 to 12 months using the classic planner layout usually only available as a wall chart. Users remember appointments, schedule holidays and plan special events.

Talking agent plugin is specially designed for eReminder 2006 - Easy Calendar & Reminder. It comes with a cast of characters including Peedy, Merlin, Genie, and Robby. If you specify Popup an agent as a reminder way, then an Microsoft Agent will pop up and read the notification when the appointment/task is due. To install this plugin, you need install eReminder 2006 firstly.

It's About Time is a new and different time tracking and billing application. Organize your days, keep track of contacts and create detailed invoices for your time. Use the dockable windows feature to customize your interface. It?s About Time will remember for next time just how you like your layout. Create an individual profile containing all of your presets, clients, and contacts.

Users of Microsoft® Outlook® will welcome this utility. It displays appointments and tasks on your desktop so you don't loose track. The desktop image remains fully visible.
If you feel that your Outlook-Calendar is too many clicks away or you are loosing your appointments out of sight, then this fully customizable Desktop Calendar is the solution. It runs in the system tray and can display your calendar in weekly, 5-day or monthly view.

Resource Management and Scheduling Software. Eliminate your Spreadsheets Today!
Simple, high-level resource and project scheduling with project and resource forecasting and flexible calendar views. With Web Resource, you can add unlimited resources, allocate these resources to projects and tasks, then view the results either on screen or in printed reports.

eReminder is a full-featured calendar application designed specifically for planning, managing, and scheduling your important dates and times. It runs in the background, sits in the system tray, and makes it nearly impossible to forget birthdays, anniversaries, holidays, appointments, meetings, and other important events. What's more, it provides plenty of reminding ways:play music, execute application, send Email, reboot PC, etc.

MicroCalendar is a Windows system tray popup calendar. It is small, unobtrusive, and always ready so you can easily check calendar dates without messing up your computer's system time or having to use a resource-intensive application. Features an attractive user interface, a tray icon that shows today's date, displayable week numbers, copy-date-to-clipboard, and form persistence (remembers where you put it last on your screen).

eReminder is a full-featured calendar application designed specifically for planning, managing, and scheduling your important dates and times. It runs in the background, sits in the system tray, and makes it nearly impossible to forget birthdays, anniversaries, holidays, appointments, meetings, and other important events. What's more, it provides plenty of reminding ways, and provides an easy way to share your data with Microsoft Outlook.

eReminder is a full-featured calendar application designed specifically for planning, managing, and scheduling your important dates and times. It runs in the background, and makes it nearly impossible to forget birthdays, anniversaries, holidays, appointments, meetings, and other important events. What's more, it provides plenty of reminding ways, and an easy way to share your data with Microsoft Outlook, Project/Project Server and QuickBooks.

Share Microsoft Outlook calendar, contact, and task information with this affordable Exchange alternative. Makes Outlook calendar sharing and Outlook group calendar scheduling easy. Works with Microsoft Outlook 2000, XP, and 2003.

OfficeCalendar creates Outlook calendar share folders under each user's main calendar folder along with a Outlook group calendar.

Free trial available.