I don't recall Pokerstars ever having good freerolls, but I do remember before Black Friday that FullTilt (before PokerStars bought them out) had the absolute best freerolls. That was when I was just starting to play online so the timing was perfect for me.
Pokerstars did have some really good freerolls, but they all disappeared 4 years ago, to the day actually.
There was a $2k freeroll on Saturdays and Sundays and to get tickets you entered the Astronomer freerolls (Hubble, Galileo, Copernicus, etc.). Each astronmer game was different, Stud, Stud Hi/Lo, 2-7 single draw, Badugi, Razz, Omaha and more. These were really easy to get tickets from as most of the field had no idea how to play these oddball games.
There was also the $100k VIP freerolls, which were $1k freerolls that ran 4 times a day with rebuys and an add-on ($0.30 each) which swelled the prize pool.
The tickets were free if you were Chromestar or higher but if you were bronzestar you could get 30 days of entries if you deposited $10 or more.
Each level had a weekly freeroll too, I think Chromestar was $5k.
I'm sure there were other freerolls, but these were long term freerolls that had been around a while.