1. Beautiful Widgets
Arguably, the most well-known widget on Android is the Clock & Weather widget from HTC, but that's obviously limited to HTC devices. The best universal Android widget that does the same thing is the one from Beautiful Widgets, which also offers the same functionality in a variety of differences sizes and configurations and tosses in a few bonus widgets such as a battery monitor and some configuration toggles.
If you'd prefer to view this as a list instead of a photo gallery, then see the companion blog post.