While Pure Calendar is an excellent choice I would also like to mention Android Pro Widgets (APW). You can get the basic version for Free and that might be enough for your needs but if not they have a Pro License Key (for only $0.50 more than Pure) that will unlock some features such as customization/themes and the app also comes with multiple widgets including both Calendar views, Bookmarks, Contacts, Social, and Messaging. Have a look.
What about Agenda Widget for Android by Everybody all the time. One of the must-haves that I enjoyed with it was combining Touchdown's secure calendar along with the Android calendar. So configurable even God gets confused.
BTW, the developer of Pure Calendar widget wrote (in September, 2010) that scrolling under HTC Sense wasn't possible. That's a showstopper for HTC Sense users. Was that incorrect, or is it static under HTC sense 3.x, or on the HTC Sense 4 on the One [X|S] ?