It is now possible to share a folder very easily in Leopard. Right or control-click, and choose Get Info from the contextual menu (or just press Command-I). In the dialog, there's a new checkbox called "Shared Folder" If you check this, the folder and its contents are instantly shared.
[robg adds: You'll still need to set up user access for this folder, using either the Sharing & Permissions section of the Get Info window, or the File Sharing section of the Sharing System Preferences panel.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071101120150563