I use this for invoices in my homegrown invoicing system. I also have a script for generating PDF & HTML versions of my resume from the source data, and the PDF version goes through LaTeX. If you're using Ruby, prawn is a nice solution also, but my favorite is going via LaTeX.
Agreed. LaTeX is the best (well, least-worst) report generating system, mostly because of its extensive ecosystem. It's well-supported in multiple languages, and there are packages for just about everything.