Besides Wikipedia that you already mentioned, my most commonly used ones are:
fp https://packages.fedoraproject.org/search?query=%s
fs https://fedorapeople.org/groups/schedule/f-%s/f-%s-key-tasks.html
gh https://github.com/search?q=%s&ref=opensearch
cve https://nvd.nist.gov/vuln/detail/%s
man https://www.mankier.com/?q=%s
pypi https://pypi.org/search/?q=%s