cssload.net lets you create CSS preloaders, and have them previewed right on your browser. All you have to do is to select a CSS animation template from the eight that are provided, choose the two colors you want the preloader to have and then pick both a size and a speed for the preloader itself to spin. You'll be able to click on the "Generate Preview" button to see how would it all work in practice, and if the results are indeed good then merely clicking where it reads "Get Code" will let you get the code snippet you should use to have the spinner or bar you've devised actually implemented. Registration not required.