My team has people on East Coast, West Coast, Asia and Europe.
The simple stuff:
* As kls said, everything goes into a ticket
* virtual water cooler (yammer) to allow collab with other teams
* web-based code review tools
* when ever possible IM or phone is preferred method of communication
The hard stuff:
Overcome cultural differences regarding office politics, work ethic etc for workers outside of the USA. If you can get a good team leader on the other side of the pond who really "get's it", pay that person well. S/he will have more leverage with people and be able to get the message across better.
We've also gone against the norm and really kept high expectations for our "off shore" folks and given then big responsibilities. We want them to become great designers and coders and be able to work independent.