Which widgets do you use and why?
If you know right off hand, then try to include information about the available dimensions for each widget, measured in tiles. (In other words, since one home screen is a 4x4 grid, then a widget that takes up the entire with of the screen and half of its height is a 4x2 widget.) Also, please state which Android version you use, preferably including your device model.
As I mentioned previously, I'm using an HTC Droid Eris that's running Android 2.1. Here are the widgets that I'm using at the moment...
Facebook (4x2) - Get this widget by downloading the official Facebook app. I just prefer this one because it's clean and simple, and it obviously gives me a quick look at my friends' most recent updates.
Twitter (4x1, 4x2) - I really don't care much for Twitter, myself, but I follow Swery65, who developed Deadly Premonition for Xbox 360, and his posts are just really entertaining. This widget lets me easily check his latest posts.
WxWidget (1x1, 2x2, 4x1) - Get this widget by downloading The Weather Channel. I like it because it follows your location, and the app, itself, has a much cleaner interface than some other weather apps. Plus, the 4x1 widget (the one that I use) has a multi-day forecast at a glance.