I have been assigned the task to build a catalog of products / on-line shop
What technology would you use to create a product listing + left sidebar filters like this one?
Well I'd use PHP / MYSQL / JQUERY / HTML / CSS combination. I've built serveral online shops like that.
The particular example you've given was built with ASP.NET, so that's another alternative. Another option would be Ruby (on Rails).
It depends on what you already know, all of the above are capable of doing what you want. Some don't like PHP because it's open source, but hey, even Facebook is built with php!