> Is there any example, tutorial, paper or swiki page about how to
> serialize instance objects in Squeak ?

This might be much more sophisticated than what you are looking for:

http://wiki.cs.uiuc.edu/CampSmalltalk/Binary+standard+for+object+interchange

Simpler alternatives are available in the Squeak image itself. Look at 
the classes in the category "System-Object Storage".

ImageSegments (see the class comment) are very interesting, but the 
simpler SmartRefStream might solve your problem.

-- Jecel
P.S.: nice to see some more Smalltalking in Brasil