The absolute core of the Hood build above is Power Attack and if going for a Dragoon feel then add
Leap Attack, perhaps with
Shock Trooper's Heedless Charge maneuver or even
Battle Jump if Forgotten Realms stuff is allowed. A list of further boosts to that include the Lion Spirit Totem ACF for barbarians from Complete Champion page 46 that grants the Pounce ability, which allows a full attack on a charge; the Rhino's Rush spell for paladins and rangers that doubles the damage done on the first attack of a charge (Spell Compendium 176); or the paladin's Charging Smite ACF from PHB 2 page 53 that allows the paladin to deal an additional 2 points of damage per paladin level (in addition to the normal Smite damage) on a charge attack, but the paladin does not gain the service of a mount. Paladins also get access to the
Awesome Smite and
Divine Might feats, if you're leaning towards a sect of paladins devoted to taking out evil dragons, such as a group of paladins who worship Bahamut for example.
The simplest build would likely be fighter 6 who took Power Attack and Weapon Focus (spear or polearm of choice) at 1st level, then put max ranks in Jump until reaching 6th level where he could take Leap Attack, and maybe take
Leap of the Heavens to make the Jump check easier. Improved Bull Rush going into Shock Trooper could be added by level 6. Combine those and a base 16 strength with a plain +1 weapon, and Weapon Specialization if you'd like for the extra +2, and if the character hit then the damage from PA would be 24 (4 x 6), plus the 2 from WS, and plus 4 for strength wielding a two-handed weapon with 16 str, plus the 1d8+1 for the base magical longspear. So 1d8 + 31 damage if it was just Power Attack, Weapon Focus, Weapon Specialization, Leap Attack, and Leap of the Heavens. Note that setting up a charge like that is usually a whole different matter.
One of the unique weapons that is exactly along the dragoon line is the Halberd of Vaulting from the Arms and Equipment Guide. It's 3.0 so I'm not sure if you'd allow it, and even then the fact that it grants a +30 to jump might be too much, but taking it down a bit won't be the end of the world. Basically if the character wielding it can make a jump of at least 5 feet high during a charge, the charge deals double damage.
As always, use (or change) any of those suggestions as you feel might be appropriate.
This is assuming doubling the damage of Power Attack via Leap Attack is close enough to doubling the charge damage from being mounted that lances allow for. Note that if you still want some mounted charge options, there is the
Spirited Charge feat in the PHB that allows dealing triple damage with a lance while mounted. I recall it's possible to get flying mounts and charge in the air with them too, so fighting dragons that way could work.
