Here are some things I have done in my career to foster good relationships, help build the brand and explain what I do.
Talk: When I worked for a larger company I would walk around every morning and talk to people. See how it was going, what they were working on and offer to help where I could. This is hard because as an In House Designer I had a full schedule, but I thought it was important. Another advantage is sometimes I could see things coming that I needed to get ready for and spot possible problems, like brand issues. I'd like nothing more than to crawl into my cubicle, put my IPod on and zone out, but sometimes grabbing a cup of coffee and heading down the cubicle rows can be rewarding.
Cheer Lead: I'd love to claim this idea as mine but it was our HR managers. We got an old monitor and computer and put it up in the main hall. I sent emails out asking what people were doing outside work. I got hobbies, baby and wedding announcements and garage sales, etc. I also asked for sales info and new deals the sales team was working on. I used a looping powerpoint show, if I had an old Mac I would have used Keynote. It played on the monitor all day and people would stop and check it out. I also did slides about using the right logo and font, and I made sure the presentation fit the company brand. This gave me contact with all the other departments and helped reinforce the brand.
Push Info: A weekly newsletter is another fun way to get info out and have a reason to make contact with other departments. In one issue I did a story about the new fountain in front of the building that looked like a satellite dish. I retouched a photo of aliens by the fountain and said they were putting a communications device in front of the building. People loved it and would stop by and ask how I did it. It was fun, got people to talk to me and gave me the opportunity to show a little of my photoshop skills.
Communicate: When ever possible tell people what you're doing and if you can, show some science behind it. Color psychology, why you wanted an image facing a certain direction to pull the readers eye in that direction. Share articles about why a strong brand is so important. Make them understand what you do is not just your whim. Show them the method behind your madness.
Pro-Bono: Help someone with a garage sale flyer, or side business, you might even get a freelance customer out of it. I did a logo for a fellow employee that was starting an online storage business. In trade he gave me some storage space, but the people that came by and commented about how they liked the logo, and gave me an opportunity to share why I did it was the real benefit.
Be sure to check with your boss to make sure they are okay with all of these, You don't want them feeling like you're undermining them or being distracted from your job. As crappy as it is, designers have to deal with the reality of office politics all to often.
An interesting post in the Pushing Rock Blog on this topic.
Have fun making new friends and explaining your skills.