Gnasty's Loot. This music perfectly embodies the stage's "You've pretty much reached 100% Completion, Spyro. But it's not over, you're almost there: your final stretch is going to be fun." kind of feeling.
Dark Hollow. Despite its name, it's an amazingly calm theme for a nighttime stage, and almost manages to evoke some kind of "summer nights" feeling.
Wizard Peak. This kickass BGM, just like Gnasty's Loot above, has a very "Let's have fun!" feeling.
Even though it was a brutal That One Level, Tree Tops had incredibly fitting and awesome background music. The way the music seems to climb towards the middle before dropping back down perfectly captures the feel of those supercharge challenges that we all love so much.
Even more music goodness includes Lofty Castle, a whimsical, yet "dangerous-feeling" theme, and Haunted Towers, which does pretty much the same.
The main theme of Spyro the Dragon, heard on the title screen, and its moody remix heard in Toasty and the Gnorc Gnexus.