A somewhat odd bunch of them:
saras97: Hostel mailing list. And my oldest one. Easy enough to explain.
putscheme: This one flickered for one glorious New England summer (of 2001). Bunch of us used to hang out day in and day out, was used to plan trips to Cape Cod, Gloucester, parties and so on. Now defunct.
siripuram: Childhood Andhra University quarters gang. The people on this know me since I was yeh tall.
ebazm: Urdu poetry and such. Subhanallah!
iitmaa1997: Boring alumni thing.
minstrelsd: The super list of the now sadly dead Wondering Minstrels
timpany: The school where I studied till 7th class. When it's alive, it's one the most entertaining ones.
Bunch of quizzing lists: Slightly boring. Good for planning trips.
irfca: Indian Railways Fan Clubs Association. To be expected, non?
marinemammalsofindia: Marine mammals of India. It's vitally important to know what's afoot in Talai Mannar, apparently.
wachusett2003: Another short lived glorious New England winter list that we used to plan weekday snowboarding trips from the office!
BSAP: Birdwatchers Society of Andhra Pradesh
There's also a bunch of others I can't find on the Yahoogroups page but I keep receiving emails from: Chennai Runners, Andaman and Nicobar Environmental Team, IIT-M's wildlife club Prakriti, and so on.