If you have resources, share them! In fact, even if you don't have any to recommend, see the Ripe for Additions page for sifting through low-hanging fruit with many resources that just need to be sorted through. Once you have a resource to add, first check whether it generally fits in line with the Coarse Guidelines. If it does, and if it's a resource that falls under the umbrella of another link, you can add it directly to that link. For example, if you find another directory of underrepresented groups in STEM, you can add it directly to the resource we link to on this website (which in that case means emailing the women who operate it). Likewise, if you find a free science textbook, you can add it directly to the Free Ebook Foundation's repository that we link to in the Overview of Free Online Learning.
If a resource doesn't fall under such an umbrella, then you should add it here! That might be a meta-resource, like for example finding a database of all the resources one should know about for teaching, in which case you could add it as its own subsection. Otherwise, you can add the resource to one of the meta-resources that are unique to the site. For example, if you find an experimental stimulus set that doesn't fall under linguistics, computer vision, or face databases, you can add it directly to the page Everything Else. To do so, either fork and send a pull request to the underlying code (located here, and each page includes a button at the bottom to edit that very page), send a message over Slack, or send an email to jdolgin [at] wustl.edu.
As a thank you for contributing, we keep a running tally here of everyone's contributions, whether they contributed via GitHub or not. Ultimately, this website is for everyone in the field (and perhaps will be useful to people in related fields). The more people who contribute, the better the resource for everyone.