Update: You can directly install userscripts as extension in latest Google Chrome versions.
In the Development Channel, Chrome adds the ability for users to add extensions to the browser, however extensions are not enabled by default and you will have to specify some startup parameters to them. To enable extensions in Google Chrome, follow the simple steps listed below: Step 1: Download the latest development channel for Google Chrome . Step 2: Navigate to the folder where Google chrome installs itself. In Windows XP Google Chrome will be installed in C:\Documents and Settings\UserName\Local Settings\Application Data\Google\Chrome\ directory. In Windows Vista Google Chrome will be installed in C:\Users\UserName\AppData\Local\Google\Chrome\ directory. Step 3: Create a folder named User Scripts inside the default folder, this is the folder where Greasemonkey scripts will be stored. Step 4: The last step is to modify the Google Chrome shortcut—or any Chrome “application” shortcuts—to include the –enable-user-scripts switch after the executable path.
With these steps you will be able to run user scripts in Google Chrome.