For the most part web developers spend our time guessing what features people might want and how said features should be integrated. Frequently we guess wrong and that wastes time and sometimes frustrates users. But there are tons of users out there who also happen to be developers and they’re actively implementing new features for their favorite sites with Greasemonkey. UserScripts.org has over 6,000 scripts. That’s 6,000 features with working implementations for popular sites at no cost to those sites! Free I say.
Each one is a feature someone wanted so badly that they figured out how a site worked and then wrote working code to modify that site to implement that feature. If you’ve got a somewhat popular webapp you owe it to yourself to watch userscripts.org and google for other greasemonkey scripts for your site. Check out what people have done, see how it works, maybe the rest of your users would like that too…
Consider offering some free goodies to people who send you cool greasemonkey scripts. Even if it’s just a free t-shirt (go to CafePress and whip one up if you have to). Maybe even put up a page of user submitted scripts. Some of your own developers may even make them to implement features they wanted that may not have been appropriate for all users of your site. Just make sure to emphasize that they’re unsupported. ;)
Side note: this post was inspired by the creation of my first Greasemonkey script. It’s something for people who use Reddit and del.icio.us. Not useful to Reddit in it’s current form but the idea behind it might be very good for Reddit if expanded to support more bookmarking sites.