How about rpm -qi?
user@linux [~]# rpm -qi rpm
Name : rpm Relocations: (not relocatable)
...
Group : System Environment/Base ...
....
Works for me.
Okay, I'm bored, here are some other options:
user@linux [~]# rpm -q --qf '%{GROUP}\n' rpm
System Environment/Base
For bonus points:
user@linux [~]# rpm -q --qf '%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}: %{GROUP}\n' rpm
rpm-4.3.3-33_nonptl.el4_8.1.i386: System Environment/Base
(Yeah, it's an old EL4 virtual box. It's what I had handy, so sue me.)
And now for the whole shebang:
user@linux [~]# rpm -qa --qf '%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}: %{GROUP}\n'
redhat-logos-1.1.26-1.centos4.4.noarch: System Environment/Base
basesystem-8.0-4.noarch: System Environment/Base
libcap-1.10-20.i386: System Environment/Libraries
gmp-4.1.4-3.i386: System Environment/Libraries
keyutils-1.0-2.i386: System Environment/Base
psmisc-21.4-4.1.i386: Applications/System
zlib-1.2.1.2-1.2.i386: System Environment/Libraries
pyxf86config-0.3.19-1.i386: System Environment/Libraries
passwd-0.68-10.1.i386: System Environment/Base
...
etc.