I spend a lot of time listening to and working with music, so I thought I'd post a list of some of the more useful audio-related sites and software I use. If you know of any good resources that I've left out, please add them in the comments section.
Exact Audio Copy is a fantastic CD ripping and burning program for Windows. I use it for it's abaility to create perfect duplicate backups using CUE sheets.
AutoFLAC is a "frontend" (for lack of a better term) for EAC that automates the process of ripping to and burning from FLAC files.
abcde is a command-line ripper for Linux. It's very quick and easy to use, and used to be my preferred ripper until I began using CUE sheets.
DVD Audio Extractor is a Windows program that rips audio from DVDs to standard audio formats such as FLAC or Ogg Vorbis. This would typically be used to rip live concert DVDs so you can enjoy the music on your computer or portable audio device. Two notes should be mentioned. 1) Despite its somewhat misleading name, this does not support DVD-Audio discs (although you can usually rip the DVD-Video compatability layer). 2) It forces the use of Dynamic Range Compression on DVDs that contain this information, which is a good option to have, but can unfortunately be very noticeable and intrusive when trying to make a good backup copy. I've asked that they make this an optional feature, but they don't seem interested.
Winamp is one of the oldest and best known media players. This is still my preferred audio player for Windows.
XMMS is the de facto media player for Linux systems. It is modelled heavily on the original Winamp, and despite showing its age these days it's still a very stable and capable audio player.
amaroK is the "new hotness" of media players for KDE. It supports various backends for actual media playback (such as xine-lib), which allows it to support a very wide breadth of formats and capabilities, and also provides a very capable playlist management system. These are the two features that won me over (finally, a decent Linux media player capable of playing multi-channel Vorbis and FLAC files!). However, amaroK tends to be extremely unstable on my system. Also, while the user interface sports all of the latest eye candy, the developers seem unmotivated to add commonly available features such as ReplayGain support or even proper TRACKNUMBER support when dealing with tag information. Development is still very active, however, so I'm hopeful these issues will be addressed in the future.
foobar2000 is another audio player for Windows. Audio enthusiests tend to promote it as the end-all, be-all of audio players, but I personally find the interface rather horrid. It does, however, support a very wide variety of formats and capabilities, and includes tagging and transcoding plugins that are second to none. I use it as an audio utility rather than an audio player.
FLAC is a free, open source lossless compression codec. Lossless compression means that it's a perfect copy of the original recording, as opposed to a lossy codec which actually discards audio data in order to acheive a better compression ratio. FLAC is a great format to use for archival purposes, but it's usually impractical for use with portable audio devices.
Ogg Vorbis is a free, open source lossy compression codec. While a lossless compression codec should be used for archiving, Ogg Vorbis can still produce very high quality tracks with a much greater compression ratio.
Audacity is a powerful, cross-platform, open source audio editing application. It can be used for anything ranging from recording audio to editing and mixing existing tracks to applying effect filters.
Help and Information:
The Hydrogenaudio Forums is a fantastic resource for audio enthusiests to share the latest news and assist each other.
The Hydrogenaudio Knowledgebase should also be mentioned. This wiki is probably the most comprehensive source of computer audio related information available.
The Wikipedia article List of albums containing a hidden track is exactly what you'd expect from the title - a list of CDs that contain hidden songs, and brief instructions on how to locate them. If you know of any hidden songs not listed there, please add them! You may also want to check out HiddenSongs.com, which does essentially the same thing but provised and indexed and searchable interface.
The Internet Archive Live Music Archive contains a huge selection of live concert bootlegs available for download.