Collaboration is a virtue; practice it often.
Inside your team, you need to be collaborating with your fellows. From code reviews to answering questions to teaching/learning techniques, the people who work with others will always be more valuable than the lone wolf who buries himself in a corner.
Everyone needs teamwork across other development teams. For example, you have to coordinate releases across projects, develop coding standards, and share libraries.
This also applies throughout the technology department. You must have a strong relationship with your business analysts, quality assurance engineers, database gurus, network engineers, systems administrators, and operations.
Across the organization as well, you will find that strong relationships will help you immensely. You need to work well with marketing, sales, human resources, finance, and other departments outside of technology.
In some cases, teamwork is needed outside the company, starting with good vendor relationships, strategic partnerships, clients, and alliances. Even trade organizations and user groups come into play.
Teamwork is crucial at all levels and, thus, is a skill that you must develop to succeed in this world.