Running the Vigos Analyzer on a number of sites, and there's still quite a few that don't compress their pages. Any decent web browser from the last 10 years can handle compressed pages. Looking at my own host, they don't enable it by default: apparently I can tweak my .htaccess to fix that.
* "How to load your website faster: HTTP compression"
* Gzip compression for PHP
* Enabling DEFLATE in Apache 2.0
* Manage compression in IIS 6.0 (Windows Server 2003)
* Manage compression in IIS 7.0 (Windows Server 2008)
EDIT 12-21-2009: Found another article regarding setting IIS compression