There is no such thing as "Apache users" or "groups" (Apache user and group are determined by httpd.conf by 'User' and 'Group' directives): you are maybe referring to virtual hosts where the VH belongs to a user of the Apache group, and is user-writeable but group-readable in order to implement separation between virtual hosts.
In that case, you may want to look into cwsAdmin ( http://code.google.com/p/cwsadmin/ ) which also allows for managing classic LAMP setups.
There is also a Windows GUI (closed source), which can be remoted for a fee ( http://www.apache-gui.com/apacheconf/index.html ).
Both applications make assumptions about Apache configuration, so if you have a non-standard setup, you might want to check it through.
Otherwise, most distributions have tools to configure Apache VHosts, and so do most hosting companies' control panels.