In these days of electronic devices, with their apps and software that help you get and stay organised there is still a place for pencil, pen and paper. So along with my smartphone and iPad, I still find that the simple 3x5 index card has many practical uses. There is a quality about paper that I love. I still have notes from decades ago and there is something about the feel, firmness and flexibility of paper that has outlived the old, large and small floppy discs and CD-roms of the early digital age. 3x5s will probably still be around when memory sticks and micro cards have moved on to their next stage of development.I like to use 3x5 cards to capture and organise thoughts; make notes for talks and presentations; to carry with me as to-do lists and to file details of and from books - their original purpose of course was to index library catalogues.
I also like to use them to send notes to friends and colleagues. Heavy enough to sit on a desk they are great for short notes and personal messages and they can be popped into a small envelope to keep messages private. I find it useful to keep some in the car in case I need to leave someone a note that I called when they were out.
3x5 cards are of a size that makes them handy to keep in a pocket, purse or wallet. Their discreet size makes them practical when giving a speech as they look a lot less intimidating for an audience than walking forward with a bundle of A4 sheets. When using them for a speech I do like to make sure that they remain in the proper order so numbering is essential. Sometimes I couple them with a treasury tag, a much used device from yesteryear but now mostly used to keep batches of computer print-out paper together.
So here's a thumbs up, or more appropriately an index finger, for the 3x5 card!