I don't know if 3.0 material is allowed, but Masters of the Wild had a Shifter PrC that had a 10 level Greater Wild Shape class ability progression.
This allowed for the addition of other types of creatures: (1-Humanoid, 2-Animal, Monstrous Humanoid, 3-Beast, Plant, 4-Giant, Vermin, 5-Magical Beast, 6-Aberration, Ooze, 7-Dragon, 8-Undead, Construct, 9-Elemental, Outsider)
...and various size progressions: (1-Small, Medium, 3-Large, Tiny, 5-Diminutive, 7-Huge, 10-Gargantuan).
...and other class abilities.
No spell progression. Not required to be a Druid to enter, but it helps.