where RELEASE_1_0 and RELEASE_1_1 are the names of your tags.
You can find a little more information on cvs diff command here
plus it should be fairly simple to create a script to make report more suitbable for your needs, ex: number of files changed, created deleted etc. As far as I know the most common cvs GUI tools (wincvs and tortoise) do not provide something like this out of the box.
The most simple solution is to do a checkout with this tag somewhere. Takes a bit of disk space, though. If that bothers you, try what you get with the -p option. If this output contains file names, then you just need to filter them out.
Best Answer
About the closest you'll be able to get is with this:
cvs -q log -R -N -S -rTAGNAME
This works against local copy, it doesn't pull from the server.
EDIT:
As Ken mentioned, a slight variation will make it pull from the server, but in this situation you need to specify the module name too.
cvs -q rlog -R -N -S -rTAGNAME MODULENAME