During the Q&A, an audience member asked which of the companies would Y Combinator jump on board to fund if YC existed at the time. Jessica said it'd most likely be Hotmail.

Agreed. Hotmail is a great one. Levchin/PayPal is also very informative. Woz is more lovable than I ever knew. Ars Digita is an excellent case study in horrible outcomes (everybody came out rich, but still, it sounds ugly and painful). Joe Kraus of Excite/JotSpot is always interesting, and I read anything about him I come across...he's like a perfect study in how to keep your head in a startup.