Whether you are at home, traveling, or simply somewhere that the urge to knit over takes you, it is good to have some basic supplies to hand.
If you are a sock knitter; a small sack with sock yarn, needles to match, two stitch markers, a coil-less safety pin (in case you drop a stitch), and a pattern. A tapestry needle to close up the toe may come in handy if you are nearing the end. You can easily keep this in your car, briefcase, tote or purse for knitting on when you have time and desire.
Scarf knitters can do the same, a small bag with yarn, needles to match, two stitch markers, a coil-less safety pin ( in case you drop a stitch), and a pattern.
Any small project will do in a pinch. One thing I have been meaning to do is to put my scrap yarn, by that I mean leftovers from other projects, into bags. These bags would each contain yarn in like weights, materials and pleasing color combinations. Packed with needles to match and instructions for mitered squares. I would work these scraps as squares joining them as I made them to form a small blanket.
Alter my suggestions to suit your needs and tastes, and I bet there are endless combinations of what knitters carry with them.
Of course, sometimes when traveling you run across a great yarn store, and you want to do your part to keep these enterprises in business. So you pick out yarn, pattern, and needles and possibly start a project right there on the spot.
The possibilities for emergency knitting are endless, I have raced out to the car to get the sock in progress I keep there when I have an unexpected wait or just need a moment to sit and regroup. Small projects such as the above mentioned socks and scarves, can be enlarged to include hats, baby booties, bibs, dish cloths, or any project that you wish. One caveat may be, to choose a project that does not requires your full attention or the need to check the pattern constantly. On the other hand if you need to block out the world around you, pick a project that requires your complete focus. You never know when the need will strike.