I have been building Squeeze+Trinity live cd's for some time. I use my 
own scripts mainly as I found official Debian-Live quite difficult to 
get exactly what I wanted.

Remastersys is really good. I use it sometimes. It is designed for 
stable; a squeeze version is available but you will need to modify the 
current version.

You need installed live-initramfs 1.177-1 (get from 
snapshots.debian.org) and grub-legacy.

http://www.remastersys.com/forums/index.php?PHPSESSID=3sugievt9bg9or5p0nhlbrh4t5&topic=949.15

is worth reading.

In addition you need to hack the script live-initramfs script 
"15autologin"  (I posted details on the above link) and 
remastersys-installer.for Trinity to work properly

If there is any interest I could post here more details. My Live ISO 
(700mb) is available on request, would appreciate some testers!.