I got the idea for these on the 4th of July, but just didn't get it done. I really like the idea of giving clever players more tools to string together as they try to survive the Underworld. Yes, it brings the horrible possibility of explosives into your campaign world. To combat that I'd make these both rare and highly unstable. Oh, they're safe and reliable in small quantities, but the moment players start getting big ideas, say anything more than a backpack full of these, they have a 1 in 6 chance each turn of blowing up as a fireball.
1. Dwarven Braids - Cords of various diameter have been soaked in spirits. Will burn at varying rates per yard. Used as precision timers. (ft/yrd per round, turn, hour etc.)
2. Mine Light - Two powders that flare up brightly when in contact. Little heat or noise.
3. Dragonflies - Essentially slow, quiet bottle rockets. Used most often to carry messages over siege walls.
4. Fire Mud - When mixed with water this paste becomes so hot it will melt metals, even put divots in solid stone. Used mostly to burn through locks.
5. Cow in a Tavern, or Skräll - Clear liquid brushed on a surface. When it dries anything that touches it causes it to pop and crackle loudly (think nitrogen triiodide).
Heck, with these and Dwarven mortar, you've got some interesting stuff to put on storeroom shelves in your Dwarven Outposts besides rope and tools.