You can't fault posts like this, listing some of the top recent Python applications written for S60-powered phones. Whether you're after some very useful example code for your own Python masterpiece or just some ideas for cool freebies to install and use, from a GPS tracker to game controller to equation solver, this is a good starting point, as will be the hosting Croozeus PyS60 Applications section, as it accumulates the results of similar choices and postings. In each case, there's full source code.