So far, I've picked out a few sweet combos for the scout.
With bonus feats, a ranged attacking Scout could go Track, (3rd) Point Blank Shot, (6th) Precise Shot, (8th) Dodge, (9th) Mobility, (12th) Shot on the Run, Rapid Shot, (15th) Manyshot. At low levels, this is basically ranger-lite. At 12th level, however, you can make use of Shot on the Run to skirmish while gaining an AC bonus and maintaining cover relative to your opponent. If skirmishing is not an option, or the foe is far way, Rapid Shot comes into play. At 15th, you can move and shoot, spraying two arrows and getting a skirmish bonus on one of them, which can be a lot of damage, particularly with an elemental bow. Being a human or skipping Track can turn this into a real archery monster, although you won't be able to get Improved Shot before 15th level.
A melee version might be Track, (3rd) Dodge, (4th) Mobility, (6th) Two Weapon Fighting, (8th) Spring Attack, (9th) Two Weapon Defense, (12th), Combat Expertise, Whirlwind Attack, (15th) Weapon Finesse. Basically, this character is moving and skirmishing, and later on carries two shortswords or handaxes either for defense or for standing their ground. This character can also make a skirmishing full attack in certain exotic circumstances.
There are a number of methods of getting a full attack skirmish. One method would be a class such as Dervish that allows a full attack while moving. Another would be special kinds of attacks, such as an Animal Lord (catlord)'s charging attack, or mixing in psionic powers. If you delay your action, a Marshal could grant you a move action, and you could follow up with a full attack or whirlwind attack. If you have the sidestep feat, you could take a 5' step, ready a full attack if you move 10' or more, and if your opponent drew an AoO, you could full attack skirmish. However, most of the time, except for special charge attacks, or using a dervish dance, and so forth, regularly gaining more than one skirmish a round is difficult and not necessarily worthwhile. The extra dice of damage are nice, but you won't duplicate the AC bonus, and you'll never match a rogue for damage output.
Some of the best PrCs are Highlands Stalker (full BAB and skirmish, but requires Endurance, good for multiclassed fighter/scouts or ranger/scouts), Animal Lord (especially cat or wolf, for pounce and scent, respectively), Horizon Walker (solid hit dice and BAB, plus tons of skill bonuses, if you want to emphasize that side), Thief-Acrobat (requires evasion, allows some great uses of skirmish and tumbling), Tempest (two weapon spring attack!). However, it's a good class for taking all the way to 20, which nets you five bonus feats, a very nice skirmish, blindsight, and freedom of movement. The scout is better at scouting than is either the ranger of rogue. However, the rogue is a better damage dealer and can learn some specialized combat moves, and the ranger is a better tracker and straight up fighter.
