Is there any software that can easily create a Styled Layer Descriptor (SLD) without using a script?
Here are two more options:
You can install the GeoExt Styler extension and use it directly to set the styles.
If you have ArcGIS desktop, and want to convert from your Map Documents/ layer files to sld files without any headaches, you can use Arc2Earth. They even have a free (free as in Beer) community edition, which you can use to export the sld files of layers one at a time. As someone who is far too invested in ArcGIS desktop, I can't overstate how easy it has made my life.
You can use Tilemill. it allows you to export SLD (compatible with mapnik)
Use geoserver CSS module http://docs.geoserver.org/latest/en/user/extensions/css/index.html It creates SLD by it's own, there is no need to learn SLD.