Talk every day. I have not lived near my best friend for 9 years now but she is still it. We talk on the phone a few times a week and see each other a few times a year. You can still be as close as ever.
skype is great. you each get a webcam ( target about $30) then download skype. it is a free service and you can talk via webcam as much as you want the quaily is great and its more personal than email or phone.