Google offers the possibility to create custom search engines. I went ahead and created a custom search engine for Calc related websites. You can use this search engine from the top of every page of this website.

I´ve found it hard to decide whether to show only results from the websites I´ve selected or to have Google emphasize the selected Calc websites. In the end I´ve decided to go for the second option. This means that for certain search terms which relate to other spreadsheets, such as Excel, you will get results from Excel websites.

If you have any suggestions for the search engine, I would love to hear them from you.