As soon as I get the hang of remastering, I am planning to remaster my distro (I have MEPIS 8 now, but will switch to either 9 or 11) to do two things: install KDE Trinity (I don't like KDE 4), and remove all extraneous software: games, "toys," and specialized programs that it was peculiar to include on the liveCD in the first place (such as jbidwatcher, a program for monitoring eBay bids). Oh, and I'll try to make it fit into one CD (not one DVD). Since I don't like downloading DVD-sized distros in the first place ( DVDs cost more!), I might download the latest antiX MEPIS and modify it to my liking.

If I successfully remaster a new version of MEPIS to my specifications, I might as well try to share it online in case anyone would want it. Where would I upload a Linux distro to share it?--I've never done it before. I did some googling, but found nothing helpful.

distrowatch.com

One one could offer it on some place via a torrent.
There may be some free storage places even like MS's skydrive or a free ftp site.
Could buy some net space pretty cheap. You don't need a fqdn as long as you have an ip and port.
You could host your on web site even if you have static ip with a dynamic ip.
Many soho storage devices have a small web server in them. I have an old nas server that can be left on the network for about 7 watts.

Sourceforge.net

You could also use google-docs to upload it, in case you are more comfortable with it:
https://docs.google.com/leaf?id=0B2_...3ZDE1&hl=en_US
I don't think you (or anyone) will want to download it, i only show that its possible, and probably will remove it soon.
I did it a while ago, so it might have changed.

Else there is also:
http://www.ibiblio.org/
(besides the ones already mentioned in the previous posts)

Don't upload it anywhere. Just set up and seed a torrent.