Getting one's hands on a real old machine may not always be viable. 
   Since the general idea is to be using a computer with limited
   resources, there are ways this can be achieved through software methods 
   on modern hardware.

   Perhaps you're only looking for tips on what software to use. See the list
   below.

How-to

  Limiting RAM on OpenBSD

     * edit /etc/boot.conf
     * add: machine mem =512M
     * reboot

  Limiting RAM on Linux machines with the GRUB bootloader

     * edit /etc/default/grub
     * add/edit line GRUB_CMDLINE_LINUX="mem=512M"
     * run grub-update
     * reboot

Recommended software

   This is a list of software observed to be used by the community.

  Desktop environments/window managers

     * cwm
     * dwm
     * i3
     * lxde
     * ratpoison

  Email clients

     * alpine
     * claws-mail
     * mutt
     * sylpheed

  IRC

     * irssi
     * hexchat

  Text editors

     * nano/pico
     * leafpad
     * mousepad
     * vi/nvi/vim

  Web browsers

     * links2
     * luakit
     * lynx
     * surf-browser
     * vimb
     * w3m