The stories listed below are free to read or listen (or both), but you should definitely support the publications if you are able so that they can support the authors.
Beneath the Willow Branches, Beyond the Reach of Time by Caroline M. Yoachim (listen at StarShipSofa)
Loop by David Odle (listen at Tales to Terrify)
Daily Science Fiction also has their own list of 50+ flash stories involving time travel.
The stories below are not free, but you can see if you can snag a copy from your local library. If not, and you feel like spending a few bucks on an eBook, they are definitely worth reading.
“‘—All You Zombies—'” by Robert Heinlein (this story was run as Escape Pod episode 200, but it seems to have disappeared); adapted into the move Predestination (2014)
3 Stories from HELP FUND MY ROBOT ARMY!!! & Other Improbable Crowdfunding Projects
“Flashed Forward” by Bradley Beaulieu
“Fulfill My Destiny—and Save the World!” by Matt Forbeck
“A Practical Mechanism for Overcoming the Directionality of Temporal Flow” by David D. Levine