Welcome Patty
You'll find lots of great PD books free here on Mobile Read. They've been nicely formatted for various readers, you'll want mobi/prc format for the Kindle.
Other places I check for PD books in order of preference...
Feedbooks
Manybooks
Project Gutenberg
Google Books
Google books won't have a format for Kindle, but you can download the ePub version (if they have it) and convert it to mobi format using Calibre (free) in about 30 seconds.