This is a great list to use as a starting point. Pretty much all these mods are fantastic and in many cases have a better storyline, henchmen and effects than the OC. If I had to recommend my absolute faves:
1. Tales of Arterra - multiple henchmen and great BG2ish story
2. Dreamcatcher and Shadowlords series - long, but you really bond with your henchman
3. Wyvern Crown of Cormyr - you have to pay $5 for it, but brilliant storyline and great work from the DLA team
4. Crimson Tides of Tethyr - great henchmen and storyline