BX

1982 Citroen BX type 1(orange indicator on the front, small bumpers)
1985 Citroen BX Break introduced
1986 Citroen BX type 2 (white indicators on the front, bigger bumpers, other rearlights)
1990 Citroen BX type 3 (black and red rearlights instead of orange, red and white)


DS/ID
An history that lists the models available each year:
http://www.autoretropassion.com/ds/ds-hist.htm

Saxo

Launched around 1996:
http://www.autowelt-graz.at/m01_img/71/g1.jpg
http://upload.wikimedia.org/wikipedia/en/6/69/Citroen.saxo.bristol.750pix.jpg
(The Peugeot 106 was restyled with the same rear than the Saxo)

Restyled around 1999:
http://a.relaunch.focus.de/img_fahr/gen/K/B/HBKBAXzS2p__Pxgen_r_385xA.jpg

The sportive models (VTS, ...) had wider wheel arches.


Xantia

Launched in 1993, a little modified for the 1995 model, and restyled in 1998.

The first model had the Citroën logo on the hood, above the grill:
http://www.snoodijkauto.nl/GT-NT-77.JPG

In end of 1994 (1995 model) they make it look more like the restyled XM:
http://www.imcdb.org/images/006/104.jpg
A break was also introduced then.

In 1998 it was restyled:
http://www.contactautos.com/contact-melun/05433.jpg


XM

Launched in 1989:
http://www.imcdb.org/images/002/057.jpg

I am not really sure, but I think that they added the turn indicators on front wings around 1991.

It was restyled in 1994:
http://img428.imageshack.us/img428/2507/xm0043508db.jpg


Citroën in USA
http://www.citroenet.org.uk/foreign/usa/us-index.html