Even a plain-text tag database would be incredibly future-proof.
E.g. on Windows command line, dir /b > files.txt and then edit the list like so:
2012-08 bank statement.pdf #finances #taxes
2012-08 dvr receipt.jpg #electronics #purchases #microcenter
2012-09 jamie prescription.pdf #medical #taxes #jamie
Although a better method for initial processing would need to be found.