Creating an architects network in a large organization

Answer 1

First you need to provide immediate value to the intended participants. That may range from interesting talks (see google tech talks for an excellent example) to the triviality of a good buffet.

Then you need the participants to give the space and possibility to get to know each other. Things that come to my mind are name tags, discussion groups, an informal dinner.

Be aware though that if you, as initiator, cannot see or name the immediate value of such an enterprise, your participants won't spontaneously flock together just for the fun of it.

Answer 2

if you turn your questions around slightly you may be able to work out the answers.
List the benefits you aim to get from the architecture network.
Then investigate those in more detail.

By detailing these benefits you should be able to get a starting point for justifying to the architects and related people why they should spend time on this. (This is cruicial as typically they'll be very busy, and not the sort of people you can boss around.)

In terms of activities I would start with a new project which has slightly overlapping technologies or processes, use this as a discussion point, with related people, as well as people not directly related to talk about the solution.

I think you'll be surprised at how much overlaps, possibly not in the actual technology used, but in the processes and design methodologies which are followed.

You could kick start this type of activity by hosting it in a nice conference venue, which people will enjoy, and be able to focus on the particular problem...