I wish to map subdomains to my wordpress tags. Then when a person visits mytag.myblog.com, he should begin to see the page myblog.com/tag/mytag (without redirect, though). This can require some modification from the wordpress code and establishing "catch all subdomains" for that domain in apache. The second part should not be a problem.

I discovered a wordpress plugin that does the above mentioned for that groups. It's known as "Wordpress Subdomains" (http://wordpress.org/extend/plug ins/wordpress-subdomains/).

Does anybody are conscious of a wordpress plugin that may do that for groups and tags?

It can be done by hand with mod_rewrite:

RewriteCond %{HTTP_HOST} !^www.example.com$ [NC]
RewriteCond %{HTTP_HOST} ^(www.)?([^.]+).example.com$ [NC]
RewriteRule ^$ /file.php?item=%2 [QSA,NC]

Sure you need to produce a wildcard dns record (*.example.com), and setup an apache wildcard virtualhost, so that all dns demands map for your host, and responded because of your site in the server.