> For instance, I have a Questionnaire and QuestionnaireView, which renders
> (it's children) Polls using Vote command. How can I show this at the main
> page of my site? Or how to do this some other (proper) way?

I'm not sure but I would try:

1) Implement a method #accept: in Questionnaire

Questionnaire>>accept: aVisitor
 aVisitor visitQuestionnaire: self

2) Implement PRVisitor>>visitQuestionnaire:

PRVisitor>>visitQuestionnaire: aQuestionnaire
 self visitCase: aQuestionnaire

3) Implement PREmbeddedRender>>visitQuestionnaire:

PREmbeddedRender>>visitQuestionnaire: aQuestionnaire
 "do whatever you want with the 'html' instance variable and
'aQuestionnaire' questionnaire"
 ...