cvs commands:

anonymous access (read-only)

via cvs pserver access:
cvs -d :pserver:anonymous@www.suppressingfire.org:/var/cvs login
cvs -d :pserver:anonymous@www.suppressingfire.org:/var/cvs checkout <package>
cvs -d :pserver:anonymous@www.suppressingfire.org:/var/cvs logout
or, more simply:
export CVSROOT=:pserver:anonymous@www.suppressingfire.org:/var/cvs
cvs login
cvs checkout <package>
cvs logout


via cvsweb (web browser):
http://www.suppressingfire.org/cgi-bin/cvsweb

or viewcvs (web browser):
http://www.suppressingfire.org/cgi-bin/viewcvs.cgi


Full access (requires system account):
access via cvs server (with ssh):
export CVS_RSH=ssh
export CVSROOT=:ext:<username>@www.suppressingfire.org:/var/cvs
cvs checkout <package>
(modify source and test)
(from directory above commands were run from)
cvs add|update|remove|whatever (messages, files whatever)
cvs commit

cvs import is OK, too

local access:
export CVSROOT=/var/cvs
(same as above)

for example,

> mkdir working_dir
> export CVSROOT=/var/cvs
> export EDITOR=xemacs ;-)
> cvs checkout jacob
> cd jacob
<edit my files>
> cvs update
> cvs commit
<your editor starts, now type in a summary about what you changed and exit the editor>



Additional suggestions for Windows users:
Here are two solutions:
http://www.cvsgui.org has the windows client for CVS
There are instructions there for using SSH with the 
gui. I was unsuccesful in getting it to work.

Update!
WinCVI 1.2 works great. Just grab the latest WinCVS and TortoiseCVS
zip files from ftp://ftp.sourceforge.net/pub/sourceforge/cvsgui/.

You can use WinCVS like this. Set the Admin/Preferences
similar to this shot:





Then, you can checkout a module by right clicking on a 
directory in the WinCVS GUI, and selecting checkout.
Use settings similar to these:



Alternative:
If you want to use the explorer integration tools,
you should be able to right click on a directory 
(the one that you intend to import your cvs modules into) 
and see "CVS checkout...". Click this, and you should get
a "TortoiseCVS - Checkout module" window. 
Fill it out like this (replacing your username and module you want):



Here's what you should expect after checking out stuff from a CVS:



Alternative to the pure GUI approach:

CvsGUI (AKA wincvs) comes with the win32 
commandline version of cvs.exe. This means that the
normal usage can work in a command prompt window.
Here's what I did:

get the latest CVSGUI/WinCVS from http://cvsgui.org
get the latest SSH for windows ( ftp://ftp.ssh.com/pub/ssh works )
   (TortoiseCVS should also work here)

install both, make sure the wincvs directory and 
the ssh directory are in your path (so that cvs.exe
and ssh2.exe can be executed from anywhere)

Now try this:
C:\home>set CVS_RSH=ssh2

C:\home>set CVSROOT=:ext:burner@www.suppressingfire.org:/var/cvs

C:\home>cvs co jacob

Alternatively, you can just install cygwin from
http://sources.redhat.com/cygwin
and all the unixy stuff described above should 
work just fine.