The Trashcan on your Fedora Core desktop (tested for gnome) is actually located in ~/Trash directory. So a simple commaond as below should clear your trash:
rm -rf ~/.Trash/*

Why did I need this?
There were some files in the Trash can which I didn't have permission to clean. Most likely I used some program with root permissions which moved files to the Trash.

Why you may need this?
In NFS based systems home directory is located in the NFS server. So it might be space saving to periodically delete the Trash directory for all NFS users.