Mindshare Labs, Inc.

With this Plugin you can redirect a page in your WordPress installation to any other URL, to a page in your WordPress installation or to the first child page.
This plugin is a fork of Redirector by Ralf Hortt. It has been updated 
for WP 3.0 and does not automatically insert ‘http:’ before any custom 
redirect thus enabling use of partial URIs and query string as your 
redirect rather than fully qualified URLs.

Redirector Mod

Redirect a page to an URL or WordPress page.

LoudSkyMedia

This simple plugin permanently redirects all 404’s to the main blog URL. There may be several reasons why you might want to do this, but the primary purpose is to siphon Google Page Rank (TM) from missing pages to the homepage.

404 Redirection

Permanently redirect all 404's to the main blog URL. The primary purpose is to salvage Google PageRank (TM) from missing pages.

Redirector Mod vs 404 Redirection