You can test Chrome builds or Chromium builds. Chrome builds have the most infrastructure for analyzing crashes and reporting bugs. They also auto-update as new releases occur, which makes them a good choice for most uses. Chrome Canary is available for Windows and Mac and autoupdates daily. Other channels (dev and beta) are available.
Chromium builds do not auto-update, and do not have symbols. This makes them most useful for checking whether a claimed fix actually works. Use the following instructions to find builds: