actually Chrome already has native support for GreaseMonkey scripts since a while ago [1]. You can just install scripts directly from http://userscripts.org.
If you're a developer of scripts, or want to be able to dive into the source then it's easier to install them via Tampermonkey[1] which provides an editor. It also auto-updates greasemonkey scripts which I don't think chrome is able to do natively.
[1] http://blog.chromium.org/2010/02/40000-more-extensions.html