Here’s the Mostly Real Quotes search engine I made for my own use, and am now releasing to the public.
If I figure out how to embed the search in WordPress, I’ll do that here.
At present it searches these sites, which (unlike most quote sites) take care to verify their quotes, and in some cases investigate the sources:
wikiquote.org
twainquotes.com
drmardy.com
barrypopik.com
quoteinvestigator.com