skipping my first lecture (about week 6 - dance/drama) i was sooo guilty but the notes were on Web CT and we don't have an exam for it....
i'd say that orientation is one of the first defining moments - you get to meet lots of new people, make new friends, etc. At my uni they do these essay writing skills (if only they'd taught us that in high school, it would've saved a lot of heartache!!)
edit: oooh another thing, getting my first assignment back barely passing, realising that uni wasn't going to be like high school. and when i got marks back from other subjects (they were much better), the feeling of reassurance that i really wasn't dumb
also, only a few weeks ago, walking in on the start of a human development tutorial which was in heated discussion about "girls' provocative dress" - it was literally a screaming match!! we even had our lecturer-in-charge involved!!
(had to be there, i think
)