Provide virtual team rooms, similar in concept to IntraNets.com or Yahoo Groups, but with more real-time functionality such as a dedicated call-bridge, collaboration interfaces similar to InvisionApp.com etc.
While I know it is "always best" to meet in person, be the platform through which geographically separated people can feel as close to in-person as possible. Try to get away from the message board effect and create more of a sticky note visual environment for idea sharing and collaborative work. Encourage communication through sketches and imagery methods.
By example, take a look through a lot of the functionality found here: http://www.invisionapp.com/ (scroll down)
Now imagine instead of collaboration on screen for an interface, what you were marking up and commenting on were sketches or ideas. This would allow folks to post a comment over an area of an idea, and thus break the pattern of discussion post message boards as the interaction medium as well as open up the team to process management Agile Scrum style.