The Classes - A Summary
If you're having trouble figuring out how to put stuff in, check out the Player's Guide to Eberron, very nice placements of all the new classes introduced up until it's development.
Hexblade (CW) - A nice, balanced, and fairly interesting class, a sort of anti-paladin
Samurai (CW) - While others find it lacking, I think it's a nice option for the "knight" concept
Swashbuckler (CW) - A good balance of skills and fighting, and the first glimpse as middle saves in D&D
Favored Soul (MH, CD) - The sorcerer analogue to the cleric. A good concept for the loner priest
Spirit Shaman (CD) - Although it uses the druid spell list, the SS fills a much different role, also a sorcerer analogue
Shugenja (CD) - The divine "oriental" class, a good conversion, nice niche
Warlock (CA) - A "blaster" mage, nice class features, and a unique "spell" system
Warmage (MH, CA) - Another "blaster", but based on the Vancian magic system, one trick pony
Wu Jen (CA) - Another oriental class, a good take on new "schools" of magic
Ninja (CV) - It's a stealth killer with balance, "Real Ultimate Power" this is not
Scout (CV) - A versatile wilderness skill user, and a nice schtick, but don't forget the errata
Spellthief (CV) - Sneak Attacks, spells, and a way to screw the BBEG mage, nice combo
Healer (MH) - I wish it hadn't been left behind in the Completes, but it's still an excellent healer, not even a Radiant Servant can compare
Marshal (MH) - An excellent battlefield buffer, works great in combination with a bard to make mooks more difficult (on the BBEG's side), or a party more cohesive
Psion (XPH) - A basic psionics "mage", and a good balance. Telepath is my favorite sub-type
Psychic Warrior (XPH) - A good, balanced "fighter/mage" class, though weaker when compared to more recent offerings, it makes up for it in versatility
Soulknife (XPH) - An excellent class, a psi-monk at the mechanics level, when combined with the soulbow (CP), needs no weapons
Wilder (XPH) - While I've never seen one in play, it makes an interesting concept and is something I'd love to see in play
Archivist (HoH) - A divine wizard, I've played one, and while fun, without help from the DM, you can lose your focus and become ineffectual
Dread Necromancer (HoH) - The DN is a True Necromancer (LM) from first level, and a nice BBEG class
Ardent (CP) - Psi-Cleric, I love the execution, haven't build one yet
Divine Mind (CP) - Psi-Paladin, again, good class, but I haven't used it yet, wording can be a bit difficult on the class abilities though, took me a few read-through to grok
Lurk (CP) - A psi-rogue with all the extras. I haven't delved into too many builds, but it looks promising as a BBEG's henchman
Erudite (CP) - I wish there was an Arcane analogue to this, but as it stands, it's just very cool. I think this would make for a good BBEG or wizards replacement in a party.
Artificer (ECS) - A great class, I hope they put it in the 4.0 PHB (along with psionics), it makes an excellent 5th man or cohort
Beguiler (PH2) - An interesting concept, and a good arcane analogue to the telepath, and a good Mindbender (CA) from first level
Dragon Shaman (PH2) - More auras, breath weapons, and a link to dragons, very cool class
Duskblade (PH2) - At first glance, seems too powerful, until you realize that it's spells are just things that fighters can do with their feats. After that, it's a nice variant fighter class
Knight (PH2) - I think this makes an excellent choice for a Henchman or even a BBEG (with arcane/archer support), though difficult to play without DM guidance
As for the rest (Magic of Incarnum, Tome of Magic, Tome of Battle, etc.), they seem good and interesting, but I haven't looked close enough, or found a niche for them in my campaign, so I don't have much of an opinion, though anything that makes encounters more interesting (alternate magic systems, cool abilities) can never be a bad thing, as long as you're comfortable with what you're using.