In the vein of GTD, I have a Reference list to store sticky posts that never truly get completed.

One of these posts is Clothing Sizes, where I have a note for each member of my family (wife, kid, myself). In each note, I list not only their current clothing sizes, but also the sizes per brand (ex: Banana Republic stuff runs smaller than Old Navy).

This way, when I am out and about, I can shop for nice gifts for both of them. I can also do online shopping for myself at work -- which helps, as I can never remember my dress shirt sizes. :)