Someone asked me to take another look, so I did, and here is the absolute earliest stuff I can find.
Wedding Peach DX by e-f. Note the semi-transparent watermark in the upper left corner. Most of the work for this ep. is credited to ruzuka or devilray.
Inuyasha #1 by Fivestar. Fivestar wasn't in any larger group, I don't think (if I remember correctly).
Love Hina 1-3, Gate Keepers 1-3 by animefactory. I'm guessing it's probably a better quality re-encode made b'cos better raw sources or better encoding tools became available.
Probably the third is the most significant. File dates may not actually be the real date that the real date the file was actually released.