I've used the Netbeans form designer, which is pretty easy to use. But I've started to code my GUIs by hand again for tools. One of the things that annoys me about the form designer is that you can't change certain code without having to copy and paste the code to a .java file which means you can't go back to the form mode...
Here's another tool I use occasionally: http://goldenstudios.or.id/products/utilities/combine/index.php
it combines sprite images into a single file ready for use by your game.. It also can export to a few formats.. I'm not sure if having the sprite images side by side in one file is as great as it sounds as it doesn't let you have alot of freedom with bigger sprites, like bosses.. Is there a way around this? Maybe more empty space around each individual sprite image?
Any other tools posted here would be greatly apprechiated by me and everyone who is interested in tools for development