Andrew Hall has released his version of the Sticky Post hack for WordPress. He has acheived this by using custom post fields. Here is a short description of the plugin:
This is an alpha release of a sticky post / select custom field plugin for WordPress 1.2. In advanced editing mode, you create a custom field KEY eg ‘sticky’ and give it value 1. In whatever categories that post belongs to, it will behave as a sticky. When you want to unsticky it, delete the custom field for that post.
You can download the plugin here.
You can download the script here.
You can see an example on this blog.