There are actually ways to knit without any needles, but today we're talking about getting rid of an extra needle: the cable needle. When your cables are fairly small, you don't need the cable needle all the time. I made a cute craft yesterday (sharing the finished object Friday!) that featured fairly small cables: 3 and 4 stitches wide. It's the perfect candidate for cable needle-free knitting!
This is an intermediate-advanced technique. A basic understanding of knitting and cables helps a lot ;) .
The basic idea is that you move the yarn in front of the stitches you'd normally slip onto the cable needle (for a back cable; behind for a front cable). Instead of slipping them onto a cable needle, you just put them on your right-hand needle. Then you knit the other stitch(es) in your cable. With a bit of tricky finger work, you pick up the slipped stitches with your left needle, then take them off your right needle, twisting the stitches into the right place.
Sounds complex, doesn't it? You should probably just watch the video. ;) It's amazingly easy to do—and pretty darn hard to figure out from a written explanation!