I have said before that an essential to being homeless is having a linux bootable pendrive.
I currently use Knoppix. I think most people who are homeless would benefit from a 4gb stick. They are currently selling 512MB sticks for $5 at PPL. It would really help out if homeless people could get some for free as well. This would help people store important files (like resumes) and give people portable computing options. (Although my Linux distro of choice is Linux MINT, I find Knoppix is a great portable solution). It is not a substitute for a laptop or netbook, but it does help. You may also wish to couple the USB drive with a PlopBootManager for older systems.
The basic Knoppix distro does require some customization. It does not come with Skype or flash preinstalled, but I would highly recommend adding those. I have added both to my pen drive.
Credit again to Simpson Church at 2740 1st Avenue in Minneapolis, MN for using Ubuntu in their computer lab. The lab is open on Wedsnesday and Thursday from 1 – 6 pm.