Often designs land on my desk with customized select boxes. This is typically a big pain because you can't do much styling by default. A few years ago I got tired of rushing out half-done versions on every project and instead took a step back and created a highly configurable custom one. I forgot about it for some time, and only recently I decided to bring it back to life. I revived the git repo by adding some styles so it looks nicer out of the box, and also upgraded all the dependencies to the latest versions so it's more likely to be compatible with modern projects.
Below are some of the notable features:
Easy to style - Lastly just extend the CSS and you can make it look any way you want.
Custom scrollbar - by default custom scrollbars using jScrollPane are enabled. You can also use the default browser one, but that doesn't look nice.
Icon Support - If an option has a CSS class, that will get carried over to the generated selectbox code as a span with a classname which can then be styled.
Keyboard access - If you focus on a select, you can hit up/down, or even type in text and it will update like a regular select.
Opt Groups - Like a regular selectbox, it supports optgroups. If those are in the HTML markup, then they will show up in the custom one.
It's driven by a real selectbox, so it will pass values in forms. The way it works is that the code will find the selectbox and hide it. Then the JS will generate a fake "custom" selectbox which can be styled. All interactions are routed back to the existing selectbox though. So... if you change the custom one, the real one will be synced as well. This way when you're submitting a form with a custom select, you don't lose the value.
Interface - There are public methods for syncing the select box if it is updated, and also for disabling it. So it's pretty easy to wire it up with complex functionality.
Browser support - I tested it in Firefox, Chrome, Safari, IE7+ (with a few style tweaks IE6 will work fine too)
Hit me up if you find any issues.