Among other things:
"...the Digital Millennium Copyright Act (DMCA) of 1998 makes it illegal to manufacture or distribute circumvention tools and use those tools for infringing purposes. In the 2009 case RealNetworks v. DVD CCA, the final injunction reads, 'while it may well be fair use for an individual consumer to store a backup copy of a personally owned DVD on that individual's computer, a federal law has nonetheless made it illegal to manufacture or traffic in a device or tool that permits a consumer to make such copies.' This case made clear that manufacturing and distribution of circumvention tools was illegal, but use of those tools for non-infringing purposes, including fair use purposes, was not."
Source: Wikipedia -- http://en.wikipedia.org/wiki/Ripping
In other words, while it is legal to rip a DVD for personal use or backup, it is illegal to download any software enabling you to do so, thus defeating the purpose. Blu-ray discs are likely illegal to copy altogether. Also, copy protection on certain audio CDs may face the same issues. It is also currently illegal to create backup copies of CD-ROMs and DVD-ROMs for personal use through disc imaging utilities, even if these discs are so old that they have no way of running their included programs without actual insertion into the host computer, thus restricting the number of older programs that may be run on current laptop computers and eliminating their use almost altogether for netbooks.