As I mentioned in the thead about what bugs me about 3e, I am of the opinion that Prcs should be a last resort and that customizing the class (3.0 PHB/p.94, PHB/p.110 and UA) should generally be the first resort or occassionally a new base class. Then again, I was arguing for more use of customization since shortly after the start of 3e and don't know how many times I would throw it out as a 3rd option whenever people would say the only choices for customzation in 3.x are multiclass or Prc.
Back in the day before Monte switched his server and opened Malhavoc, I had posted several fighter variants using the Thug example as a guideline. I also posted them on the WOTC board, but lots of people were telling me that I was creating new classes :\ . Others such as Sonofapreacherman, had posted an option about allowing wizard to get a form of bard lor. And I had been using the Wilderness Rogue and, a form of Barbarian hunter long before UA.
The nice thing I find with customzation, is that it allows a character to play a lot of character concepts from first level and at the same time take some of the sting and awkward of multiclassing just the straight core classes.
My own campaign uses a lot of customized classes and some non core classes while dropping some of the PHB classes.
Barbarian: Players can chosse the PHB bararian (berzerker) or the barbarian hunter from UA (although they get Favorite Terrain instead of Favorite enemy and may choose from Archery, Two weapon fighting, or Mounted Combat)
Bard: Bards fall into 3 categories all though I working on a non-spell casting version, the Skald.
Arcane Sage(UA): modified to receive no rogue skills and a modified bard list which includes loss of healing spells.
Divine Bard: modified to lose the rogue skills and has a modified bard list which loses some of the Arcane spells.
Troubador: Closer to the PHB bard, this variant loses healing spells and has a modified spell list.
I plan to add a skald class which gets no spells, but I am still debating how I want to do this.
Cleric: All Clerics are are variants. the type of variant depends upon the deity served which also determines the cleric's specialized spell list and domains. Variants include:
Cloistered Cleric (UA)
Divine Defender (UA)
Healer (Mi HB)
Specialty Priest (e.g. the female clerics of one deity are variants of the divine defender, but give up all Armor in exchange for a Monk's unarmed AC bonus, and are limited to very few weapons in exchange for flurry of blows and the OA Shaman's unarmed attack damage).
True Druid: A cloistered cleric variant posted both on Andy's board and here on Enworld (under house rules). It tires to get the druid closer to what I view a Celtic druid
Druid: The class is dropped and replaced by the True Druid cleric variant and Green Ronin's Shaman Class.
Monk: does not exist (replaced by the specialty priest example given above).
Paladin: do not exist (replaced by the divine defender from UA)
Psychic (Green Ronin)
Ranger: Is currently included and currently fills the role of the militant arm or the nature goddess . However, I might ditch it in the future. I dislike base classes that receive late spell casting. Furthermore, I already have the wilderness scout, the ex-hunter fighter variant, and the barbarian.
Rogues 3 Variants
phb Rogue:
Thug (UA): the list has a few fighter combat feat and a lot of Rogue Feats, This allows the character to focus on various rogue archetypes that might not be sneak attack types or combat types.
Wilderness rogue: This is used for standard hunters, scouts and the old 2e outlaw kit
Shaman (Green Ronin),
sorceror: (the class itself has some small tweaks)
battle sorceror is allowed
Swashbuckler (Complete warrior)
Witch (Green Ronin)
Wizard:
militant wizard is allowed
scholar wizard: may give up bonus feats for +2 skill points (to be spent on class skills) and Sage Lore
wizard, Specialists
All PHB specialists follow the specialist options for trading feats in UA (with slight modifications-- e.g., Illusionists have no ties to Shadow in my campaign)
All PHB specialists have their own spell lists
Variants specialists from PO: Spells and Magic can be used. Each gets their own unique spell list.