I use cwm (“closed world machine” ) to aggregate and apply inference rules to my data.
I use jpegrdf to store metadata about photographs inside the photographs.
Jena is a Java library for accessing RDF graphis.
I use RDFTwig, a set of extension XSLT extension functions, to make it easier to style RDF data for presentation.
My Palm Pilot is my “personal information appliance”. I store as much data in there as I can.