NOTE: This plugin is being released as-is. It works fine for shape layers, but there are rendering issues with raster layers (like images). It can work with a lot of purging but we HIGHLY recommend that you don't use it on raster layers.
Also, Sundial is macOS only.
If those two things are not a problem for you, Sundial is a simple and free long shadow plugin. If you need something more robust or fully-functioning, we recommend Long Shadow on aescripts.