Guides:
How To Play AAC Files in WMP
http://www.afterdawn.com/guides/archive/how_to_play_aac_files.cfm
Tools:
Directshow Filters for Ogg Vorbis, Speex, Theora and FLAC :
http://www.xiph.org/dshow/
M4a/Flac/Ogg/Ape/Mpc Tag Support Plugin from the guy that wrote Tag & Rename :
http://www.softpointer.com/WMPTagSupport.htm
APE, MPC, WV, OFR, FLAC tags
http://wmptagext.sourceforge.net/
NoMousy: Hides your mouse pointer or turns it back on command line driven
http://www.apps4apps.filetap.com/nomousy.html
Cross Fader and others: The cross fader is buggy you can't use the position slider but it works.
http://dsp-worx.de/
Here is one more program to scan your files and see which ones have problems http://mp3val.sourceforge.net/
DOn't forget to add tag and rename
Here's the program I used to separate all of the bad mp3's from the good mp3's in my library, MP3Test http://www.maf-soft.de/mp3test/ (http://www.maf-soft.de/mp3test/) , except don't do what I did and choose to put them in a Damaged folder in the album directory. Under Options choose a sepatate directory for the Damaged files and check the box to keep the file structure, so all you then need to do is run MP3Test to separate the good files from the bad, point AShampoo Music Studio 3.40 http://www.download.com/Ashampoo-Music-Studio/3000-2167_4-10025639.html (http://www.download.com/Ashampoo-Music-Studio/3000-2167_4-10025639.html) (Fully Working 30 Day Trial) at the Damaged directory to fix all of the bad ones in the Damaged folder and then just copy the contents of the Damaged folder back into your good music directory and it will put all of the songs back in place (files will now be fixed and still in the correct directory structure) doing it this way will save days using AShampoo, as it doesn't need to scan the good files. Then in the future if you run across some bad files just run it through AShampoo again.
here is another one eist told me about. I used it to clean up my tags that had (,) and " in them. You just use the action section and pick what you want replaced.
http://www.mp3tag.de/en/
Might be god to make a guide in the tutorial section about cleaning up MP3 collections.