The Beyonders has orantium, an extremely volatile substance that explodes on contact with air or water. In the first book, the protagonists carry a single (rare) specimen of the stuff to serve as an Emergency Weapon, and its singular use is devastating enough to end a skirmish (with most of the combatants in pieces). In later books, the heroes find an entire arsenal of the stuff, and at one point, trick a shapeshifter into turning its entire body into orantium. The resulting blast leaves a mushroom cloud. Interestingly, nearly all of orantium's portrayal points to being an alkali metal, just on fantasy steroid.
In the finale of Darkness Visible we get Marsh throwing a bottle of pyroglycerine from the dome of St Paul's Cathedral, with predictably messy results for the crowd of bad guys below.
In Soul Music by Terry Pratchett, there's a dramatic scene near the beginning when a wooden carriage is speeding along a narrow mountain road. The carriage misses a turn and crashes far below in the canyon, exploding on impact. (With the mandatory wheel rolling away from the wreckage, which is, in accordance with ancient narrative tradition, on fire.)
Blowing anything (especially themselves) up is very much a staple of the Ankh-Morpork Alchemists' Guild. Well, that and turning lead into gold gold into less gold.
In Hogfather, the wizards of Unseen University make the ultimate hangover cure by tossing together every normal hangover cure they can think of, and three magic spells. The final ingredient, provided by Munstrum Ridcully, is Wow-Wow Sauce, a condiment that contains two-thirds of the making of gunpowder. The other wizards, seeing this trope coming, hide behind the furniture. When Ridcully upends the entire bottle, nothing happens. It's only as Ridcully is chiding his colleagues' lack of backbone when the fireball erupts.
Each of the Draconian races from Dragonlance die in...inconvenient ways, including one breed that explodes on death.
The Dresden Files: It's not a proper day in the life of Harry Dresden if something hasn't exploded. Also, the premise of one of the best Batman Cold Open beginnings ever.
Much later on, when he's told that his duel has to stay within the confines of the arena, his response is, "Well, I have this thing with buildings..."
Subverted at one point in Fleet of the Damned by Allan Cole and Chris Bunch, when an interstellar PT boat crashes and the safety mechanisms work:
Sten's hand was poised over the emergency power cutoff breaker when the ship's computer decided that it might be dying but preferred something less Wagnerian than what would happen, and beat Sten to it.
In the Harry Potter series, this is the result if the Killing Curse (Avada Kedavra) hits an inanimate object instead of its intended target, it will explode.
Played for laughs in the sports sections. Making fun at the fact that Americans Hate Soccer, they have an alternate sport to the popular wizard-esque football Quidditch: Quodpot, in which the players try to catch an explosive quaffle and not let it fall down.
In Havemercy, Royston's Talent is making things explode. He manages to state this in the wordiest way possible.
The Lord of the Rings: "Then there was a crash and a flash of flame and smoke. The waters of the Deeping-stream poured out hissing and foaming: they were choked no longer, a gaping hole was blasted in the wall."
In Project NRI, Louise and Juuri attempt to break everyone out by blowing up a window. It fails.
It's a rare Stephanie Plum book that doesn't have something (usually Stephanie's current Alleged Car) getting blown up or set on fire.
While he was generally on the side of huge explosions being a bad thing, H. Beam Piper not only nuked a major city in Uller Uprising, Space Viking (one of the most badass names in literature) featured three uses of the Bethe-cycle bomb, commonly known as the "hellburner." What does this do, you ask? This creates A MINIATURE SUN WHICH LASTS SEVERAL HOURS in the target area, destroying everything within about a thousand miles. Anyone pack the marshmallows? The craters are still smoking roughly two weeks later.
Later in the same book, during a space battle an enemy cruiser survives several hits from antiship missiles. Frustrated beyond endurance, the ship's gunner smacks it with a planetbuster bomb. The resulting explosion lit up the sky for a hemisphere of the planet they were orbiting at the time.