Anyone know if I can make a checkbox-list with all terms from a taxonomy, and search for the posts belonging to the checked terms? Listing categories in the checkboxes also would be a bonus!
I built something similar for a client not too long ago. I believe your question is if it is possible -- I can definitely say yes there. How would you go about it? Well, as I don't have the code handy, I'll give you a brief run-down of the steps I went about.
I hope this makes sense - I went on and AJAX-ified this along with a few other modifications, however this example shows the backbone on which I built this.