Also, my DM said any Prestige Class from a WotC book is a go.
I think Exotic Weapon Master 1 can land you a weapon trick to not provoke when shooting, that may be useful. It's a shame you don't use throwing weapons, Master Thrower is awesome for Rogue ranged attackers.
Beyond those, not much I can think of... Assassin is decent for any Rogue, C.Adv has two Nightsong guild classes (enforcer and infiltrator) that are occasionally useful. Deepwood Sniper is from a 3.0 supplement, Masters of the Wild, but is easily adapted to 3.5 if allowed. It's a great PrC for long ranged fighting, not sure how much it'd help you, though. Ditto for Cragtop Archer from Races of Stone.
Feats you might want (aside from the obvious choices) are:
PH2:
Crossbow Sniper
Deadeye Shot (has lots of requirements, but basically guarantees you one SA/round)
Ranged Weapon Mastery (need Weapon Specialization, and hence 4 Fighter levels)
Telling Blow (take if you make the xbow Keen; gives you SA on a crit)
Dragon Compendium v.1:
Concealed Ambush (only -10 to hide after sniping instead of -20)
Races of the Wild:
Woodland Sniper (GREAT tactical feat, need BAB +6)
Complete Adventurer:
Staggering Strike (works just fine with ranged SA, and is crazy powerful)
EDIT: Melee only, my mistake. Still useful if you plan to occasionally fight hand to hand...
All the above are conveniently listed here:
http://www.crystalkeep.com/d20/rules/DnD3.5Index-Feats.pdf
In Complete Scoundrel, there's a feat called Savvy Rogue to improve Rogue special abilities, a worthwhile feat for anyone of the class.
Finally, if you can use a feat from Song and Silence (3.0), there's an amazing feat called Quicker than the Eye. It's like Deadeye Shot, but lots less requirements, and instead of having to wait for your readied attack to come up, you just do a simple move action Bluff (or Sleight of Hand, I forget) vs. Spot to make the foe flatfooted, giving you a standard action left to SA him. It 's hard after round 1 for ranged Rogues to get SA, remember (if you want advice on other ways to get it, I can help you, most involve the Use Magic Device skill or a friendly caster).