I have already mentioned the README files, typically installed in /usr/src/linux/Documentation/cdrom/. These can be a gold mine of useful information.
The following usenet FAQs are posted periodically to news.answers and archived at Internet FTP sites such as ftp://rtfm.mit.edu/:
Several other Linux HOWTOs have useful information relevant to CD-ROM:
At least a dozen companies sell Linux distributions on CD-ROM; most of them are listed in the Distribution HOWTO.
The following Usenet news groups cover CD-ROM related topics:
The comp.os.linux newsgroups are also good sources of Linux
specific information.
There is a large archive of CD-ROM information and software at ftp://ftp.cdrom.com/pub/cdrom/.
A FAQ document on IDE and ATA devices can be found at ftp://rtfm.mit.edu/pub/usenet/news.answers/pc-hardware-faq/enhanced-IDE/ and at http://www.seagate.com/techsuppt/faq/faqlist.html.
Western Digital, the company that started the IDE protocol, has information available on the IDE protocol available on their FTP site at ftp://fission.dt.wdc.com/pub/standards/atapi.
A Web site dedicated to multimedia can be found at http://viswiz.gmd.de/MultimediaInfo/. Creative Labs has a Web site at http://www.creaf.com/.
The Linux Documentation Project has produced several books on Linux, including Linux Installation and Getting Started. These are freely available by anonymous FTP from major Linux archive sites or can be purchased in hardcopy format.
The Linux Software Map (LSM) is an invaluable reference for locating Linux software. The LSM can be found on various anonymous FTP sites, including ftp://sunsite.unc.edu/pub/Linux/docs/LSM.gz/.
The Linux mailing list has a number of "channels" dedicated to different topics. To find out how to join, send a mail message with the word "help" as the message body to majordomo@vger.rutgers.edu (Note: at time of writing these mailing lists were severely overloaded and a replacement was being sought).
Finally, a shameless plug: If you want to learn a lot more about multimedia under Linux (especially CD-ROM and sound card applications and programming), check out my book Linux Multimedia Guide, ISBN 1-56592-219-0, published by O'Reilly and Associates. For details, call 800-998-9938 in North America or check their Web site at http://www.ora.com/.