Before I post anything, I will say this. Two Steps From Hell
makes nothing but epic music. Seriously. I'll post a few of my favorites, but I recommend looking up everything of theirs, because it's amazing.
Heart of Courage
The MOST EPIC
battle or reveal you will ever make. Unfortunately, it's kind of short, so some may prefer the fan-edited (and well done) longer version
. It takes longer to get to its most epic, though.
The town theme from Diablo, and it rocks. Works in pretty much any town or while traveling.
More Two Steps From Hell
, this one is definitely an "Epic reveal" kind of song, maybe for the amazing ancient city you designed.
Somebody already posted half of the RotK soundtrack, but somehow missed this one. Good for a chase scene or something.
Night Ride Across the Caucasus
Loreena McKennitt is a great Celtic-style musician. This could be if you want a really entrancing bard to be at your tavern, or perhaps if the party is spending a night among elves.
EDIT: Just a thought, maybe go through and sort the songs into categories. General Epicness, Battle, Travel, Town, etc.