Well, “on a budget” only if you’re already using Confluence.
I recently took on a team of my own at work and wanted to implement a Kanban board for us to organize around. I heard the FLOSS Weekly episode a couple weeks back which featured the devs from Taiga.io. I took a look at this and even signed up for a fee hosted account to demo it. Very nice software, but it occurred to me that there’s a task macro in Confluence that I’ve used on occasion in the past. So I created a new page in our private space, inserted some columns with task macros; one for Backlog, one for In Progress, and one for Done. It’s not fancy by any means, and is certainly not scalable beyond the few of us, but it’s getting the job done for now and only took a few minutes and no additional $$$ to setup i.e. no budget approval.
It’s likely that there’s similar solutions in other CMS systems. If you think something up, let me know.