I'm not familiar with the "crunchbang" so I can't tell you exactly which distribution-specific utility you use to trim the system resource usage down. (For example, I'm using OpenSUSE so I would use YaST). In general, you can go into the /etc/rc.d directory tree and manipulate the symbolic links that are used to start services at boot time. To avoid running a service the simplest -- and least destructive (IMHO) -- way to turn it off would be to rename the symbolic link and make it hidden. For example, to turn off the NFS daemon", you would
mv S08fs .S08nfs
Renaming the link preserves it in the startup directory but removes it from the list of steps that the system startup scripts will "see". And it makes it easier to turn the service back on if you decide you need it in the future. (I assume that you're running this system at level "3" and don't need the graphical interface running all the time. If you do, do the above in the "rc5.d" directory as well. However, for a pure server, you would probably be better off running at level 3 and using X Windows by running "startx" only as needed.)
What to turn off? I'd guess that NFS might not be necessary. Also look at any multimedia-related daemons as candidates for disabling. You may find after doing this tweaking that the amount of resources you free up aren't as large as you might think. But every little bit helps. (I think the Linux installers
require a lot more resources than the resulting Linux system they create. Slide shows and Tetris games to keep you amused during the install process are so-o-o necessary, you know. :^( )
Hope this helps...