IrfanView is simply the best free graphic editor available. I use it primarily to crop odd-sized images into a 4:3 ratio for my desktop wallpapers and screensavers. It even allows you to create your own screensaver (.scr file) from your favorite images. It also has a screen capture function and can extract individual images from animated gif files.
IrfanView can also function as more than just an image processor. By loading some free plug-in programs, you can view flash video (.flv) and shockwave (.swf) files as well as listen to .mp3 audio files. It does not have playlist capability, so it would not serve well as your primary audio program; however, it remains an extremely versatile program capable of running one-at-a-time tests on a wide variety of file formats.
While it might not be as polished as some of the professional software packages for which you pay a king's ransom, IrfanView is a top-notch program that is a real value for the money—because it is absolutely free.
Winamp is the best media player for music in mp3 format. You can create and save your own playlists and select from a wide variety of skins to customize Winamp's appearance to suit your own taste. Winamp also comes with Gracenote, an on-line music search feature that can update an mp3 file's ID3 tag fields with relevant information about the song (e.g., artist, album, track number, release date, genre, etc.) I find that Gracenote works about 75% of the time. It returns totally false information about 5% of the time, and the rest of the time it returns information from greatest hits compilation albums, not the original release. Despite these shortcomings, it is well worth having. Winamp is not just an mp3 music player; it handles a wide range of both audio and video file types, including flash video (.flv).
Winamp was originally written by a company called Nullsoft which is now a subsidiary of AOL. Since there is no telling how long AOL will be around, it is worthwhile to have a backup in case Winamp is longer offered for free. Here are two alternatives. Both play not only .mp3 music files but also—unlike Windows Media Player—.flv video files popularized by YouTube.
Found a video clip of your favorite artist playing your favorite song but want to convert it to mp3 format for your music player? Quick Media Player might be for you. It occasionally encounters codecs it cannot handle, but it is still a versatile program that converts an impressive variety of audio and video file types. FLV Converter, as its name implies, operates only on flash video (.flv) file input. Don't be misled, though: it converts .flv files to any number of different output formats. And perhaps because it specializes in processing just .flv files, it seems to do a far better job handling the codecs that seem to thwart Quick Media Converter.
I first heard of Audacity a long time ago, but I cannot for the life of me explain why I never tried it before now because it dovetails perfectly with my affinity for open source software. Audacity is a marvelous cross-platform (Windows, Mac, Linux) audio editor. I especially like the fact that it provides both visual as well as audio cues to mark the desired sound segments.
I use Audacity primarily to crop out prolonged silence, annoying hisses, and unwanted advertisements at the beginning or ending of my mp3s. I also use it to crop the beginning riffs to some of my favorite songs (e.g., Bob Jovi's Wanted Dead or Alive) and then convert the result from mp3 to wav format so I can then use the clip as my Windows startup sound.
Important Note: To save (or more accurately, "export") any file to mp3 format—even a file originally in mp3 format but which you have edited in any way— you must first download a separate-but-still-free add-on called LAME mp3 encoder written specifically for Audacity. Fear not: LAME is very easy to install and well worth the effort. [Added 21 May 2011]