Beta Epsilon chapter - 1995 (I was there
)
National philanthropy - Chaim Sheba Medical Center in Israel, the Elizabeth Glaser Pediatric AIDS Foundation
Time commitment - weekly meetings, rush-related activities, and activities in support of the big annual charity fundraiser are the minimum, but there is so much more going on, including social activities, other philanthropy work, committees, offices, etc. You get out of it what you put into it.
How about this - What local charities or philanthropies do you support? My chapter supports the General Israel Orphans' Home for Girls - this was the philanthropy of the local sorority my chapter was founded from. (A lot of my sisters say "orphanage" instead of "orphans' home" - this was drilled into us as a big no-no.)