Our shop does a lot of work for higher education, especially the "home environment" and large-scale sites. And while sitemaps, workflow diagrams and schematics are helpful for our internal team (and the more web-savvy client teams), in general the abstraction works against us. I find that clients tend to gloss over sitemaps and just agree with us to keep the project moving, not realizing how crucial this step is to overall IA. They can't visualize that the site map turns into the navigation until they see it in a comp (wireframe or design). They also can't envision how linking works until they are able to actually click through a prototype. That's where ProtoShare has changed everything for us. I no longer bother showing sitemaps to clients. I go right to interactive wireframes with minimal styling to show them how it "works." They get it much sooner, provide better feedback, and now we're able to engage them in getting content attached to these comps much sooner -- which may be the biggest improvement of all.