http://cdimage.debian.org/cdimage/archive/
QUOTE:
Some user-provided 2.0, 2.1 and 2.2 images (Hamm, Slink, Potato)
3.0_r0 to 3.0_r6 (Woody)
3.1_r0 to 3.1_r8 (Sarge)
4.0_r0 to 4.0_r9 (Etch)
5.0.0 to 5.0.10 (Lenny)
6.0.0 to 6.0.10 (Squeeze)
7.0.0 to 7.11.0 (Wheezy)
8.0.0 to 8.11.0 (Jessie)
8.11.1 (Jessie LTS, for some arches only)
9.0.0 to ... (Stretch)