InsaneJournal

Rainlendar Desktop Calender
Rainlendar is a neat little calendar program suitable for casual users. If you want to keep track of things like trips, appointments, deadlines, etc, this is the calendar for you. It runs right on your desktop over your wallpaper and can notify you of upcoming events. Place your cursor over the date and a tool-tip balloon appears with all events for that day. Once it loads, it doesn't appear to effect computer speed, and it is sleek, attractive, and easy to use. It's also skin-able, although I like the default skin just fine. And, of course, it's FREE! Get it here.

Update: There is a simple and beautiful new skin available that I really love. It's called Tinted Rainy and it will match any wallpaper or theme. It also has a small calender mode which shows the current date and the clock. Get this skin here.

As you can see in the screen-shots below, this skin works beautifully no matter what background you use.