Let's cut to the chase: CalWidget, by Egg ‘n Stone, is on my short list of must-have applications. As the name implies, it is simply a calendar widget that goes on your home screen and displays your upcoming appointments. If you rely on your calendar at all, this is one of the first things you should download from Android Market.
CalWidget goes far above and beyond what the built-in calendar's widget does. The built-in widget displays only your next appointment, and that's it. CalWidget is much smarter. It displays as many of your upcoming appointments as will fit. It comes in a dozen different sizes. You are free to choose which one you would like to use, so you decide if it takes up just a couple of cells, or one entire screen. Personally, I find the 2x2 size to be a good balance. It displays my next four or five upcoming calendar events and takes up only one quarter of a screen.
CalWidget also gives you a ton of options for how it looks and functions. By default, touching the widget will bring up options to refresh, go to your main calendar, or open settings. You can change that, though, so that when you click it, it will go straight to your main calendar. I like that option, because then it can replace the calendar icon on my home screen (just make sure you are happy with your settings first). You also have a ton of options to customize the layout, the date format, the colors, and the opacity of the background, which means you can really get it to look just how you want.
You're even covered if you have multiple calendars. You can choose which calendars you would or wouldn't like to have appear in the widget. All this for free.
Conclusion: It's all pros and no cons for CalWidget. It's literally one of the first apps I suggest people download, and it's one of the very few I recommend without reservation. Egg ‘n Stone also makes the wonderful Profiles app, and they have done it again with CalWidget.