One thing that Windows lacks is decent calendar. Active Desktop Calendar is a fully customizable calendar which features notes, tasks, alarms, and merges neatly into whatever desktop wallpaper you have.
One of the best features about this calendar is that it allows you to share dates and data with others on your network. It also integrates with Outlook so that your appointments and tasks are displayed clearly on your desktop.
You can even make it synchronize with your PDA via Outlook.
The calendar is fairly customizable. There are several options for changing calendar icons, fonts and colors, marking weekdays of choice and marking dates with notes and/or alarms.
If you find the calendar is running slowly or slowing your system down, you can also revert to a text only version of the calendar. If you need hard copies of your important dates, there's also a very easy to use print option for calendar data.
Although it's not necessary, there's also a world clock screen saver that shows your computer's system time, plus five major time zones around the world.
All in all, this is an excellent calendar although it's going to find it hard with things such as Google Calendar which are accessible from anywhere.
