Or, things I’ve had to Google while using R.
Easily extract data from graphs
I use this tool all the time to (roughly) measure means, standard errors, etc. in plots I find online.
Confirm that your visualizations are accessible to people with color-blindness
Upload images of your plots to this website to check how people with different types of color-blindness perceive your chosen color palettes.
This website helped me identify a few academic papers related to perceptual restoration that I had overlooked during my literature search.
Statistics walk-throughs for SPSS
When I’ve had to do statistics in SPSS, this website has been beyond useful. At some point you’ll hit a paywall, but I find the free content to be usually sufficient. This link goes to their page on Pearson correlations.