A worker co-operative seems like the ideal corporate structure for the typical consulting software shop. It can be set up to be very corporate-like or it can be set up as a loose group of freelancers who pooled together to share a health insurance plan, or anything in between.
My company (http://nomad.coop/) operates in a similar fashion. We all work under the Nomad umbrella, are equal partners in the company (a requirement for being a coop) and work together on freelance projects as we need to. We've been together for around four years and it's worked incredibly well for us.
