Google Chrome, unlike Firefox, where the Greasemonkey extension is needed to install and use userscripts, supports userscripts out of the box. The browser is however not fully compatible at this point which means that several userscripts will not work properly if they make use of functions that the Chrome browser is not supporting or actively blocking.
The two Chrome extensions Tampermonkey and Blank Canvas aim to reduce the amount of non-working scripts by adding support for some of the functions to Chrome that are not available by default.
Tampermonkey was the first Chrome extension to increase userscript support in the web browser. It adds support for several userscript functions like GM_registerMenuCommand or GM_xmlhttpRequest which are not supported by default.
The extension will also intercept the install dialogs on the userscript website.
This provides additional information about each userscript including its version and website's that it is configured to work on.
Userscripts that are installed while Tampermonkey is running will not be added to the Extensions listing of the browser. They are instead listed in the options of the Tampermonkey extension.
Here it is possible to select a script from the list of installed userscripts to take a look at its source code and configure compatibility options.
Blank Canvas is another extension for Chrome that changes the way userscripts are handled in the web browser. The extension is in a very early stage according to the developer, basically an alpha version which does not yet offer the same functionality as Tampermonkey.
Installed userscripts are on the other hand displayed in a handy table that displays information such as names, versions, sites, features and controls.
The controls can be used to easily edit, enable / disable or delete userscripts that have been installed.
Blank Canvas offers a clearly superior layout to manage userscripts in Google Chrome while Tampermonkey leads compatibility wise.
Update: Black Canvas has been removed by the author from the official Google Web Store. Tampermonkey remains as an alternative on the browser.