Work on CollectionBuilder projects involves manipulating metadata and digital files. This page lists some open source tools that might help your workflow when preparing collection contents – beyond the software used in building the site.
OpenRefine is a free and open source “power tool for working with messy data”. It is great for exploring, cleaning, and transforming data. If you have extensive work to transform existing metadata or description into something for use in CollectionBuilder, this might be the tool you need!
LibreOffice is a free and open source office application suite (similar to Microsoft Office). “Calc” is their fully featured spreadsheet app (similar to Excel). Calc can correctly import and create UTF-8 CSVs (unlike Excel).
GIMP is a free and open source image editing application (similar to PhotoShop). It is a powerful, fully featured, and high quality editor that can edit any image format and do batch processing.