Heroes Of Might & Magic: In The Wake Of Gods
I found this fan-made add on for HOMM3 few weeks ago and I'm playing it since. It's what HOMM3 should be.IT IS FREE!!!!
http://www.strategyplanet.com/homm/wog/download.shtml
at first it's quite complicated but you get used to it (read the features that goes with it).
You can modify absolutly everything in the game (creature dwelling, extra skills, new units, commander units,...),every unit has it's own experiance
Only downfall is that you need HOMM3:Complete