I there website with other users project created in after effects ?
I'm looking after a Waving flag, created without any plug-ins.......
I don't know any websites with other users project, but www.videocopilot.net/tutorials/ has some cool stuff.
As for the flag, there's something here: http://library.creativecow.net/articles/lindeboom_kathlyn/flag_freeform.php
People upload and share projects on the After Effects Exchange.
The tutorial from Kathlyn Lindeboom that MadsRH points to uses Forge FreeForm, so I don't think that that's going to help the original poster if he's looking to do this without any additional plug-ins.