The other thing is clubs and societies market day, where you can shop around for clubs and funnily enough societies you would like to join. You could find out about and join clubs even if you don't go to the market, but it could be a bit of a hassle for you, and there wouldn't be any free lollies. This goes nearly all day.
Will you be working 9-5? If not, there will probably be things on around the times you have off. The study skills centre does a morning long talk about student life and studying, which is quite good, but not vital. They run some free courses during semester anyway, which are probably more overly worthwhile.
The other 'serious' sort of event is faculty/subject talks, but these generally just go over degree plans, majors and tell you to ask for help if you need it, that sort of thing.
Mainly O-Week is to get you feeling familiar with the place. The freebies aren't that good, unless you go in for calico bags.