ChromeDriver Canary has the latest new ChromeDriver features. New binaries are built and made available multiple times a day.
Be aware, it's designed for developers and early adopters and can sometimes break down completely.
Starting with M115 the latest Chrome + ChromeDriver releases per release channel, including Canary, are available at the Chrome for Testing availability dashboard. For automated version downloading one can use the convenient JSON endpoints.
For earlier versions, you can find the Canary builds as follows:
It's generally a good idea to pick the latest build. In each of those folders,
there is a file named LAST_CHANGE, that you can use to find the latest build
number. Open one of the Canary builds, dependent on your system
architecture, and type LAST_CHANGE in the filter box near the top. It may take
the site some time to locate the file (up to a minute). When the LAST_CHANGE
file link appears, click it to download the file, and find a build number
inside it. Then type that build number into the filter box, and click the
folder link that appears.