In universities, how to team up with your colleagues? Many times in universities, people don't dedicate much time to build friendly relationships with colleagues. 
Unfortunately, this happens both in the tenured positions and in non-tenured positions, with many bad consequences (such as for examples, many researchers actually don't know what other colleagues are researching on...).

I've always been thinking that building strong friend relationships with colleagues can be very useful and powerful, for careers but most of all to create a more serene work environment. 

I think that a good way to create friendly relationships with colleagues is organizing extra-work activities, such as dinners, soccer matches, etc.
Last week some of my PhD student colleagues organized a pizza dinner between colleagues. All my department (~150) PhD students were invited, but in the end we were just 9! :-(

What d'you do to build strong friend relationships with colleagues?
Could you tell some success stories?
Could you give some good advices?
In our department, the assistant professors go out for drinks once a month (a fixed day of the week and a fixed week of the month). That tends to work out quite well: we can let off steam, compare notes on our students (and what senior faculty dish out in the name of advice :)), and generally get a nice group. I've had a few collaborations start because of this as well. 

The general faculty also do a drinks night occasionally, but not as regularly.