A website carbon calculator. Plug in a URL and it'll give you a breakdown of the estimated emissions for a single visit and return visits, and gives an monthly estimate based on your visitor numbers. A tool I hope to make more use of.
Similar to Lowww Carbon, this is another lightweight, climate-friendly website showcase. They benchmark per-visit emissions against an average calculated from the HTTP archive. You can find out more about their method on the site. Another fantastic resource.
A showcase of low carbon websites. Grades each site based on its carbon footprint, gives you an estimation of the emissions, and breaks down some case studies. Great resource!
A fantastic resource for web design inspiration. Free and paid tiers, allows you to search via many criteria, and even separates out the various component types. Couldn't do without it.