They're taken alongside the standard classes and have their own progression; thus, you could have Wizard 10/Archmage 5, Cleric 4/Champion 1, so on and so forth.
There could be an argument for them just being a group of abilities that you choose from a list, though.
Anyways, here's my votes:
- We Built This City (On Rock and Roll)
- The Mythic Journey
- Missing a Common Sense
- Saying Goodbye
- P.S. I Hate You
- All that we see or seem is but a dream within a dream
- Third Law
- Hey, I know that _____!