Particle Builder is a nice tool for creating and testing cool particle effects with Cocos2d.
It comes with lots of rockin features including fullscreen preview, different background colors, quick properties menu for immediate preview, extended properties menu, saving and loading your work, FPS display, ability to apply movement to your particle systems...
You can also freely retrieve your particle systems by mail, with the choice between two different file formats, for use in your own programs.
As for the particle properties themselves, well you have access to all of them. Blend modes, colors, spin, emission type & rate, position type, gravity properties, radius properties... none is missing.
Not forgetting the texture, which you can chose among your OWN images.
Help files are also included in every screen to help you out and explain how each property influences your particle system.
With Particle Builder, not only will you be able to test your particle systems in every matter and in simplicity, but you will also learn how to use all the available properties to achieve what you have in mind.
After that, using the particles in your own games and programs will be reduced to two lines of code.