Exact Audio Copy
There are lots of free programs around that call themselves CD rippers, but if you're serious about making the best possible copies of your discs, you need Exact Audio Copy. As its name implies, this free software makes perfect bit-for-bit copies of your discs, so you don't lose data – and therefore quality – when the tracks are transferred to your PC or an external drive.
Even if you don't plan to go entirely disc-free, it's well worth making backups with Exact Audio Copy for when the physical media inevitably picks up scratches.
Why you need it
Exact Audio Copy uses a technology called AccurateRip, which uses data from other users around the world to determine whether there are any errors in your ripped files caused by dirt or damage to the discs. AccurateRip can also correct for imperfections created by your optical drive as it reads the CD.
Once you've made your copies and stored them in a lossless format like FLAC, you can keep them safely archived, and create copies in your preferred lossy format for everyday use.
If you need a hand getting started, audiophile forum Head-Fi has an excellent guide for new users.
Download here: Exact Audio Copy