Do you need to do something repetitive on your browser? iMacros from Iopus can help you do those task automatically. It's comes as a Firefox's extension, so you can install it very easy by downloading the .xpi file and open it using Firefox's menubar. Actually, this extension is used for web automation and web testing tools, but you do lot more than just for testing purposes. By supporting macro, you can ask for repetitive actions to be done automatically by the browser. You can use several programming language to create a macro, for example Python, Perl, Java, or even FoxPro.
Check the demo page if you are new to this kind of extension.