How the heck does one search for user shared scripts in this GeoNet world? I found some 2011 discussions about how ArcScripts was replaced by script galleries over at ArcGIS.com, but I didn't find much there.
Paul I gave up a long time ago trying to see what was on...or where there was..a list of current scripts. I am currently waiting for ArcScripts 2.0 like many other people. I did manage to locate and bookmark all the scripts I managed to post but dissecting the URL is fruitless, you are sent to the ArcGIS home page and from there you need to "search" for what you want http://www.arcgis.com/home/ good luck.
Alternately you can try Esri's github site... Esri GitHub | Open Source and Example Projects from the Esri Developer Platform which is as equally dense.
I don't believe there is an organized place to post tools on GeoNet world, though code can be posted there.
I agree with Dan Patterson that current place to look for such things is http://arcgis.com. But it is not easy to find things by just entering stuff in the search box. If you first click the search box, select Tools and enter search terms in the box, you can do a lot better.
For example, here's the URL that is generated when I do this and search for "python toolbox":
You also may want start at the ArcGIS.com Analysis and Geoprocessing Tool Gallery and search within that group (another search option dangled off the search box).
When I clicked on the example URL for python toolbox I got 0 results. It seems you have to be logged in for the search to work. After I logged in that same URL (search) resulted in 40 hits.