I've set up an iPXE boot system which allows me to boot in to several different environments over the network (using HTTP!).

The stock iPXE iso is ~1MB, and can be run without modification. E.g. download the image, put it on a thumb drive (as in, dd if=ipxe.iso of=/dev/sdX), boot it and use iPXE commands to connect to our apt server for further instructions. Specifically:
1) boot the machine
2) almost instantly, you'll see "Press Ctrl-B for the iPXE command line..." - do it and you'll be an iPXE command prompt.
3) enter the command 'dhcp' (without quotes) and wait until you get an 'ok' and get returned to the iPXE prompt
4) enter the command 'chain http://${server-path-to}/boot.ipxe' and you'll get a curses based boot menu.

From here, make your choice and begin. Current menu items are: install various Ubuntu LTS setups, Spinrite, and GParted. I'm working on adding a security distro (like BackBox or NST), but it isn't ready yet.

The iPXE scripts and menus all came from the iPXE site. It requires a bit of effort to familiarize yourself with the way things work, but isn't too difficult to get up and running quickly.