Set Parameters from User Input Is there a way to set parameters from front-end user input?

Let's say I have a page that displays a list of entries. On that page, I have a form select called paidStatus with options notReceived, received, and paid; and another form select called order with options asc and desc.

Then, in my template code, I want to grab the list of entries:

{% for entry in craft.entries.section('sectionName').order('postDate post.order').find() if entry.paidStatus == post.paidStatus %}

with order and entryStatus being populated from the submitted form selects. That way I can change the criteria used to generate the list of entries on the fly.
Yes, you can pass in a variable into the parameters and to get the query string values use craft.request.getQuery().

I can recommend this blog post by Jérôme Coupé for a great introduction to setting up the form and the criteria model filters:

Combined searches and filters using Craft

You should also have a look at other questions tagged with "form".