Many of these, such as those old cover CDs, should just be thrown out. Mostly this is software trial editions from years gone by and small samples of data, usually from a community in which I have no interest.
Some CDs contain resources I do refer to from time to time. It's just frustrating that they sit there occupying desk top space I could better use.
Strike up the band, marching in comes ... .iso ... which is a format that allows you to keep exact image files of whole data CDs, not music or video CDs, on your hard drive or other electronic storage medium. I've now started a project to copy some of that more valuable CD data.
Even if you're like me and work with a three-year-old laptop you probably still have plenty of space left on your hard drive. There's even more on a USB connected external drive on which I do an automatic backup every day. If you have that storage space which you've already paid for why not let it earn its keep?
To do so you need two pieces of software, one to convert the contents of the CD to an .iso file on your hard drive, the other to allow you to access that file from your computer just as if it was a CD in the physical drive. I found free versions for both purposes.
To move CD contents to an .iso file I'm using ISO Recorder, downloaded from http://isorecorder.alexfeinman.com/isorecorder.htm. It seems to work well without any issues so far.
To use an .iso file you need software to mount and dismount the file, just as you would insert and remove a CD from its drive. I use Virtual CloneDrive found at www.slysoft.com/en/virtual-clonedrive.html. It's one of the disk imaging utilities suggested at Lifehacker http://lifehacker.com/5660244/five-best-disk-image-tools. I did have a bit of trouble with the installation and sought help from instructional videos found by searching
I'm not suggesting these two pieces of software are the best, just that they work for me.
Now that I have everything installed I'm finding that often it's quicker to search on the virtual drive than the CD, plus I'm not spending time searching through a pile of CDs to find the one I want. You do need to preserve, or destroy, the CD. Selling it or giving it away contravenes copyright if you're still using the copy.