Something you might be able to do with local alums (and those away who would be able to travel) is planning a picnic.  I haven't been able to go to any of my chapter gatherings so far, but I know they do a shopping trip every few months.  We also have a few Mary Kay reps and candle lite reps who host parties from time to time.  
Pinkyphimu's mention of a listserve is a great idea.  The one set up by a member of my chapter has put a lot of us back in touch, which is great.
I'm a lil curious about the yahoogroups... the one I found isn't very active.  Am I missing some that are national and more active?  I think I'll have to check that out.