Lockdown mode is a feature that you can use to secure published sites. When lockdown mode is turned on, fine-grain permissions for the limited access permission level are reduced. The following table details the default permissions of the limited access permission level and the reduced permissions when lockdown mode is turned on.

Enable lockdown

Disable lockdown

A little more than a year ago Bill English wrote a post about 3th party MOSS tools that I just came across.
It's an old post, but still a nice read if you are interested in adding functionality to your MOSS deployment in one of the following categories:

1. Collaboration
2. Security, User Account Management and Permissions Management
3. Search and Relevance
4. Workflows
5. Document Administration
6. Upgrade and Moving Content

The post can be found here: http://admincompanion.mindsharp.com/BillBlog/Lists/Posts/Post.aspx?ID=75