Foobar2000
-Full UTF8/16 support (unicode)(handles LANGUAGES)
-Masstagging, renaming, restructuring directories
-Handles extremely large collections easily (like I'm talking even for 32000 files +)
-Converts various different codepages into unicode (wtf does this mean? It means when you see !@#SDF@#$ typical for chinese/japanese/korean songs, you can convert it so it shows up proper in all programs)
-ReplayGain Support
-Gapless Playback Support
-Converts different file formats, encode files, rip cds
-Low memory footprint
-Fixes broken MP3 headers
-HIGHLY customizable, make use of your own tags, organizes your music (especially large collections!)
-By customizable, I do not just mean the functions. Its appearance can be changed practically to whatever you want it to (limited to the Visual Style) or perhaps you prefer your computer's programs to conform to the VS. You can easily make it look like WMP11/iTunes etc. Practically anything, as long as you take the time to either 1) figure out how to do it 2) find someone else's that looks like it and download their config.
-Can connect to iPod through components
-Very supportive community @ HA
I highly recommend the program!
-Only disadvantage, steep learning curve (that is, if you want to design your own layouts FROM SCRATCH. This being said, most people share their layouts and you can easily modify existing ones)