Nokia's mobile portal MOSH became a great source of free content for Symbian devices. Mosh has a lot of downloads such as themes, games, ringtones, applications, animations, videos, pictures. These files are broken into set of categories. If you haven't found desired file you can ask the community...
I've recently found an interesting free app for S60 devices - Symmy. Symmy is a VoIP communication service on Symbian S60 v2 and v3 phones. It is completely free application like Skype or other VoIP . You can call user of Symmy for free and send them instant messages.