I graduated Dec. '11. There are three things that I wish I had been told about working after college:
1. Find a mentor. If you have any flexibility in the projects you work on or the people you get to work with choose to work with someone who will be a mentor to you. I think we're all familiar with the benefits of a mentor as a teacher, but there's another important function of a mentor: they can be a "cheerleader". A good mentor will talk you up around his co-workers and management, and make sure that those who don't work directly with know that you are capable of putting out quality work and that you should be considered for more interesting/challenging work in the future.
3. Ask questions. When you start your new job you'll feel like you need to prove yourself as just as capable as everyone who's been working on the same project/codebase/technology for years. So you'll stay late banging your head against the desk trying to solve a problem that has nagged you for days. You finally breakdown and ask an experienced engineer what he thinks, he says, "Oh yeah, I've seen this a hundred times. It tricky the first time you come across it..." and then explains how to fix it in a few minutes. If you had gone to him earlier you could have increased your productivity and saved your self a headache. The more experienced engineers are a resource. If you aren't using all the resources available to you to get work done efficiently, you're not doing your job.
2. If you're unhappy with your work, speak up. Your management cannot read minds. If you find your work soul crushing but you do well on it your management will keep you there until you burnout. At that point you'll rip off your clothes and streak through the halls and your management will think, "I never saw that coming." Your company(probably) wants you to be happy because if you are you'll be more productive and that adds to there bottom line. Let your management know that you would like to do other work and they'll try to move you somewhere you can be happy. It may take time but I've found that just knowing that you management cares goes a long way to easing the pain. If your management does care, start working on your resume and browse wanted ads during lunch.