There's a wiki page on [http://wiki.debian.org/accessibility]
Starting from Etch, the debian installer comes with brltty included in official installation CD-ROMs.
It should be able to autodetect USB devices without user intervention (except pressing Enter at the syslinux of the very beginning of the boot process). Serial devices can be configured by typing the TAB key and then
at the syslinux prompt, see brltty for more details. Note: before Lenny, instead of typing the tab key, type install .
Note: the preference menu is enabled, so you can change the braille translation table on the fly at will.
If you don't have any braille device but want to test the support, you can plug a tty device on the serial port and use the TTY driver:
Up to Sarge, debian installer used to include some "access" floppies that hold a speakup kernel. They could be found on usual debian cd image mirrors, in /debian/dists/stable/main/installer-i386/current/images/floppy/access/ for installing a stable distribution on i386, for instance. For instance, [ftp://ftp.debian.org/debian/dists/sarge/main/installer-i386/current/images/floppy/access/]
Use those images to generate floppies (thanks to dd or rawrite). Start the computer with the one holding boot.img.
Then the installer will prompt your for a "drivers" disk. Either use cd-driver.img for installation via CD or DVD, or net-drivers.img for installation via network.
There are also images on [http://people.debian.org/~shane/] .
Etch does not have these "access" floppies any more. Lenny, however, has speakup again, on the CD images which have the gtk installer, which for x86 is all of netinst, businesscard, and cd1s. Netboot images ("mini") may or may not have it depending on how they were built.
Boot the CD, wait for the syslinux prompt, type the down arrow key once to select the GTK flavor (except on the netboot ("mini") gtk image since it only has it), press the TAB key and then
press Enter, after some time you should hear the debian installer.
When using the USB stick method, you do not get a menu. Just put the speakup.synth=yourdriver parameter at the end of the `append' line of syslinux.cfg
Note: the weekly builds for Squeeze also have it.
Note: the daily builds on [http://people.debian.org/~joeyh/d-i/images/daily/netboot/] don't include the gtk installer and thus don't have speakup.
Note: there is experimental support for software synthesis in the espeakup images on [http://people.debian.org/~sthibault/] . Just boot them and it should talk!
Note: a remaster-append.sh script is available on [http://people.debian.org/~sthibault/], it permits one to remaster a syslinux iso image to append some kernel options to avoid having to type them at boot, typically a speakup option for instance. Pressing the down arrow key and enter is still needed however.
Some hardware devices directly peek text from the video memory. You can use the regular debian install CD with them, provided that you type install debian-installer/framebuffer=false at the syslinux prompt. The installer will then run in text mode and the hardware device will work.