What is another source for Dashboard widgets?
The widget download page was a curated approach to enabling a single place to locate and install widgets from.  Developers would submit a Widget and associated details and host the file for downloads.

The lack of updates is down to 1 of 2 things:  1) Apple stopped accepting additions and ammendments to the listings, 2) Developers stopped submitting updates.

Both are probably true, and certainly a lot of developers stopped writing widgets in order to write iOS apps and such like instead, at least according to the anecdotal information I am aware of.

However, the listings as they stand are useful for identifying good widgets, just because no updates are listed doesn't mean none are available.  I searched for Time Machine Buddy which is a useful widget I use.  It's still listed, but at an older version on the Apple site.  However the link to the developer is included which allows me to check and download an updated version direct from the developer.

Unlike iOS apps, widgets can be hosted and downloaded from anywhere, they didn;t have to go onto the Apple site alone.  So you can use the directory to find interesting things, and then hit the developers direct to find updated version.

If a download link is dead, or the developer is no more, you can still find the download site useful to get the name of a widget, and then use tools like osx.iusethis.com to search for alternatives.