Races of Stone (ISBN 0-7869-3278-3) is a Splatbook that focuses on Dwarfes, Gnomes, and the new race, golaiths. It has many new features for the game, but the meat of the book is in the feats section.
Blade Bravo A gnome version of dualist, its 10th level ability is great, but the rest of the class is just so so. Cragtop Archer The quintessential sniper class. Deepwarden A char-op classic, 2nd level gives you con to ac, full BAB, d12 hd, 6+skills. Great class even without optimization. Divine Prankster Full caster progression with nice skills. It's 10th level ability is nice, but by then you'll have better spells. Runesmith At first it looks like just another armored PRC, but then you realize that ONE level duplicated 10 levels of spellsword. Removing arcane spell failure all together. Shadowcraft Mage One of the oddest PRC's in the game, on top of some spiffy illusion abilities, you can amplify your illusions with shadow essence. Making this the only case where a FAILED save does more damage. Stonedeath Assasin An underdark assasin, good to get hide in plain sight quickly.
Exotic Armor/Shield Proficiency - Gain proficiency with one of the great armors in this book.
Heavy Armor Optimization/Greater Heavy Armor Optimization - Reduce the Armor Check Penalty and increase the Armor Class of a suit of armor.
Reckless Rage - An additional -2 AC, and +2 Str, +2 Con while raging.
Steady Concentration - Always take 10 on Concentration Checks. - Vital for Master of the Unseen Hand, and other arcane builds.
Trivial Knowledge - Roll Knowledge checks twice, taking the higher of the two checks. - Great with Bardic Knack or just normal skill monkeys. Has a good synergy with the Knowledge Devotion feat from Complete Champion.