While the stable channel of Google Chrome is still on version # 18.0.1025.168, Chromium and Canary build have touched the mark of version number 21. Google releases Chrome in four different channels: Stable, Beta, Dev and Canary. Apart from these releases, users can install Chromium, the open source browser behind Chrome, as well. Chromium comes without several proprietary features of Chrome and does not update automatically similar to Chrome and several other browsers.
Chrome 21 will receive many exciting features and stability fixes before it releases as stable version. New features already landed in Chrome 21 include a new default (pre-installed) app for Google Docs.
Other changes recently introduced in Chromium/WebKit include new Media Gallery Extension API, support for tab-size CSS property, support for intent HMTL tag etc. For more information on Web Intents, refer the latest W3C draft here.
Chrome Canary build can be downloaded from here, while for the latest Chromium build on Windows 32-bit platform, visit this page and choose the most recent build at the bottom. These pre-release versions are not suitable for regular web browsing and should be used only for testing and development purposes.