Product sorting:

It will be great if I can put to product group some values and user can sort in frontend by this product group values.
Also product sorting by price (ASC/DESC) / by manufacturer.
Comparing two or more products in one category.
In the first page can be newest or products with special price or special offer.

I agree, sorting would be fine.

You should try out this contribution http://www.opencart.com/contribution/in ... tion_id/27

and the additional comments on usage here http://forum.opencart.com/index.php/top ... ml#msg3898