I asked about making this in the General Thoughts thread, and it looked like enough of you were interested to warrant its creation.
So without further ado, I present the Karaoke Thread!
~*[General Thread Guidelines]*~
1. Professional and non-professional covers are welcome. To elaborate, if you have a program like Audacity and a professional-grade microphone with which to record, go for it! If you have a crappy microphone and a program that just lets you record background music really muted in the background, go for it! I'm with you guys.

2. A cappella covers are also totally welcome. Go for it.
3. As far as song content, I would suggest referring to forum rules. However, as far as I'm personally concerned, since it's a song and it's not like it's your words, if there's a song you really like that happens to curse a few times and happens to involve sex (because let's be honest, what popular English song nowadays ISN'T about sex?), I won't mind.
4. Songs don't have to be iDOLM@STER related.
5. You can sing in any language. Sing in Swahili or Russian or Welsh or Korean or English or whatever your heart desires.
6. You can use instrumental tracks.
7. A website I can recommend to those of you who just want to sing a cappella is vocaroo.com, which is a voice recording site.
Take warning, though: links to your uploads on this site DO expire after a time and WILL erase your work, so if you plan to keep this thing forever, I suggest using something more reliable. It is great for something you just want to do really quickly, though.
I might update that list as I remember stuff or people make suggestions.
~*[Personal Guidelines That Apply Only To Me That Are Mildly Important To Your Understanding Of Stuff I Do]*~
1. Covers tagged [iPad] were recorded on my iPad using a program that lets me record instrumental tracks in the background JUST loud enough for it to actually make sense.
2. Covers tagged [A Cappella] were recorded without instrumentals using a fancy microphone.
3. Covers tagged [Professional] were recorded using a fancy microphone AND Audacity.
3.5. I don't actually own a fancy microphone yet so I won't actually be recording anything tagged [A Cappella] or [Professional] yet.4. If a song is tagged with a name ([Marsha], [Haru], etc.), that song is sung in the voices of one of my characters because I sing in character voices a lot. If a song is not tagged with any name, I sang it in my natural voice.
Everything else is unimportant/up to you. :U
Go wild and have fun, guys!
I'll be adding something myself eventually :U