I carry a spindle of CDs to work with me so I have enough music to last me through the day. It's usually just a random collection of 20 or so CDs. It's kind of bulky, though, and the plastic shell is kind of flimsy; it obviously wasn't meant for using over and over, just for holding a new stack of
blank discs.
I sometimes also carry a small 10-disc nylon carrying case (with the CDs in separate plastic sleeves), which is a bit of a hassle, since each slot has to be changed individually.
So I thought to myself, what's stopping me from having the best of both worlds--the portability and durability of the case, with the stacking power and ease of CD swapping of the spindle? It would look a lot more like the nylon carrying case, but when you unzip and open it, it just has a hard plastic casing and a short spindle stick to thread through the middle of CDs. To keep it a nice size, I'd recommend it hold about a dozen CDs. Also, when you close the case, it snaps the spindle stick gently into place to hold your music/CD-ROMs in place.