When I graduated I participated in quite a few assessment centre style interviews. This was a full day with some written tests, some group activities as well as normal one on one interviews. You also get a good feel about the organisation that you will be joining from this kind of day.
Initially it seems quite stressful with lots of competition, but big organisations take lots of graduates every year so in the end I had some fun and enjoyed it.
Applying for lots of posts and attending lots of interviews helped me decide whether the organisation was right for me or not.