Possible? Yes. On an individual class basis, it's pretty easy, even.
Basically, you just take the class you want to put a "prestige" gloss on, give it some appropriate requirements (that can be met at 5th level), and compress the benefits into a shorter span of levels. 4 level casters (such as the Paladin or Ranger) get 8/15 caster advancement, 6 level casters (such as the Bard) get 11/15 caster advancement, and full casters (such as the Druid) get 15/15 advancement.
E.g., Suppose, for instance, I want to make the Druid a PrC.
Requirements: Knoweledge(Nature) 8 ranks, Ability to cast 3rd level Divine Spells, Plant and Animal domains (need both), alignment within one step of neutral.
HD: d8
Skill Points: 4 + Int per level
Class Skills: As standard Druid
Saves: Good Fort, Will; poor Reflex
Benefits:
1st: Nature Casting, Druid's Oath, Animal Companion, Wild Empathy
2nd: Woodland Stride, Trackless Step, Resist Nature's Lure
3rd: Wild Shape 2/day, Spontaneous Summoning
4th: Wild Shape 3/day, Large Wild Shape
5th: Venom Immunity, Wild Shape 4/day
6th+: As Druid class features of five levels higher - e.g., Wild Shape Tiny (Druid-11) at PrC Druid 6, A Thousand Faces (Druid-13) at PrC Druid-8, and so on.
Nature Casting: The Druid spell list is added to your Cleric spell list.
Druid's Oath: the standard Druidic requirements
Spontaneous Summoning: Can convert prepared spells into Summon Nature's Ally Spells of the same level
Others: Exactly as listed in the Druid list, except you add your Cleric and Druid levels together to determine your effective Druid level for whatever it is.
At the end, all that's really changed from a standard Druid is that the Prestige Druid is missing out on 16 skill points, has an extra domain spell slot, has a few weak turning/rebuking attempts, and can spontaneously cast Inflict or Cure spells. If you like, you can even have one feature "turn off" another - e.g., when you gain Spontaneous Summoning, you lose Spontaneous Cure/Inflict spells.
You end up with a slightly different power curve (it'll generally be slightly higher - you have all the features of the "Druid" class, and the first five levels of features of the Cleric class) but you've got essentially the same one.