Greasy Scripts allows you to search for user scripts available for the site you're just visiting with a single click. You can also choose to be automatically notified whenever scripts are available for a page.
Currently Greasy Scripts searches the popular scripts repository Greasy Fork. More repositories are likely to be added in future.
Greasy Scripts integrates nicely with Greasemonkey and Scriptish if you have either of them installed, but you can also use it on its own.
With this functionality Greasy Scripts fills the gap that was left when the former number one page "userscripts.org" went off-line for good and the add-on Greasfire (which had a similar feature set but was limited to that page) became obsolete.