I talk to my big sis almost every day.  My little works so much that we only get to talk about once or twice a week.  (Both my big and little are in San Antonio and I am in Corpus Christi)
As far as the whole chapter, we have a summer contact list with phone numbers and addresses.  We all keep in contact via e-mail / AIM / MSN messenger.  The gals back in San Antonio are planning biweekly get-togethers, but for us who are out of town 

 we can't make them all.  They try to have the get-togethers on the weekends so that the sisters who are out of town have the opportunity to head to San Antonio for a sisterhood weekend.