I came across this great little webpart while researching for a [DEAD LINK] project. It displays time around the world, and also gives you the weather conditions at the different locations. It lets you search for the locations you want to display, and collects data from their webservice. It is highly configurable both design- and feature wise, and best of all - it's FREE
The webpart is made by a company called Bamboo Solutions, and it can be downloaded here.
Here's a screenshot I found online:
And here's a screenshot from my test environment: