You RULE, xdesi!!! Thanks for stickin with me.
It's called Exec-PHP and it worked like a friggin' CHARM!!!
In summary, with your help I am now able to hide/mask posts of specific categories on my home page by adding this to index.php:
<?php if (is_home()) { query_posts("cat=-20"); } ?> to index.php.
And I can replace the default Recent Posts widget with a customizable one that lets me show or hide posts by categories.
1) Install the Exec-PHP plug-in.
2) Add this to the "text box" widget:
<?php query_posts('cat=-20'); ?>
<li>
<h2>Recent Posts</h2>
<ul>
<?php while (have_posts()) : the_post(); ?>
<li><a href='<?php the_permalink() ?>'><?php the_title(); ?></a></li>
<?php endwhile; ?>
</ul>
</li>
This going to let me build my entire site, blog and non-blog, on WordPress, and create certain content of my 'site' as posts instead of pages, where I decide that's appropriate.
Damn, I just thought of my next issue: having posts of certain categories (i.e. press releases, job postings) not be part of my RSS feed. If you have any thoughts on that I'd appreciate it, but I'll probably spin this off as yet another 'wordpress as a cms' thread since the ones I've found say "do your site and blog as one instance" but don't address these problems.