Shoestring budget or not, Dark Reading has published an edu security guide to finding your data. It is basically a shortlist of software:

It’s possible to get a jump-start on discovering sensitive data using freely available and open source tools — provided that you understand what your company needs to identify and protect. The tools range in functionality from simple searching of files on desktops and laptops to spidering and searching Website content.

I would be more impressed if he had gone to the trouble of explaining how to script and then automate the tools into a SIEM.