The code for doing servlets in VisualWorks Smalltalk is already out there.
Have a look at WhiteCap (http://www.jdmsoft.com/WhiteCap.html), which
implements the Java Servlet Specification version 2.2. This is for VW, not
Squeak, but I'm sure it could be ported. 

Perhaps you could try it using the non-commercial version of VisualWorks to
see if it's what you want before porting it to Squeak, although having a
Squeak port would be useful as well. :)

Aaron