All you need to do with .m4a files, is to rename them .mp3

Jack: I added you to my favorites, but can't read your name because the background is black.

UFF, Here they are. The conversion was a breeze - took about 3 seconds per song. But the upload was a pain in the butt. And I did not realize the limit of 12 songs at first. So I had converted a lot more. But that's for next time then. http://whs.muxtape.com/

Ya mysticgeek, I followed your recommendation after jd clarified this matter of free and fee. It is super simple to use and I did not realize that it would convert a file in a couple of seconds. Awsome! Thank you again. The muxtape setup, however, is a little lengthy and it is too bad that you cannot chain several songs together for upload - at least I did not see that option.

@Bartman that is cuz Jack is a crazy evil Metal Head! LOL!

We need more people to post their Muxtape!

@mysticgeek, is there a way to make a second and third tape on Muxtape? I was trying to make one from my classical music collection, but I do not see the option for more than 1. And if I sign in with a second user id, they will probably reject me on the basis of the email address. I guess I could trick it with one of my other emails.

To edit a track you can use e.g. Magix Music Cleaning which I once bought. You can also try with Windows Movie Maker. Just import the music and snip away.
As to the 20MB - it looks to me that this is total. Because when I started uploading it said that I had room for 15 songs (I guess based on the size of the first song). But when I was all done, there was only room for 12.

I believe it's 24 MB per song. I have 12 songs that range from 3 to 6MB each in my tape.

I think Bartman is right. It must be more than 20MB's. When I add all my songs it is closer to 40MB. But it says about the 24MB per song.