Monero has a BuildBot that automatically compiles the latest Monero builds for multiple operating systems here. I cannot find an option to actually download these builds. For instance, suppose I want to download the latest build of Kovri for Windows x64. How can I do this?
You can download the files for the build you would like to examine under the "Steps and Logfiles" section. For Windows, you will often find a .zip file. The file you can download is underlined in red.
Not all builds will have files you can download and run.
Finally, since these are not official releases, they may not be stable or as safe as official releases. Use these only for testing purposes with care, not for storing any Monero.