1. Prue has the least amount of screen time and possibly is the sister who was captured the most number of times. In Apocalypse, Not (season 2), she was pulled into another portal and only seen at the start and end of the show as well. 
In Bride of Gloom (season 3),  she was captured to be the bride of Zile, appearing only at the start and about 3/4 into the show (where she fights her sisters).
In Look Who's Barking (season 3) where she was turned into a dog, appearing only at the start and the end of the show. 

2. Piper died the most number of times. 
In Awakened (season 2), she contracted sort of like an incurable disease and Leo was unable to save her because he was not allowed to see her. However she was cured in the end. 
In Wrestling With Demons (season 3) she was nearly killed by the principal of the Demon's Academy by a machine of some kind. Again, Leo healed her but that took an awful long time. 
Next in Coyote Piper (season 3), Prue had to drive a knife through her heart to release Terra from Piper. 
Finally in All Hell Breaks Loose (season 3), she was killed by a bullet through her stomach by a witch wannabe. 
I also believe she was killed in season 1's Deja Vu All Over Again. This makes the number of times Piper died 5 times.

3. Phoebe turned bad the most number of times. 
In season 1 (Is There a Woogy In The House), she was possessed by the Woogyman and tried to kill her sisters. 
In season 3, she was affected by the marriage of Prue to the warlock and became evil in Bride and Gloom, and turned into a banshee in Look Who's Barking. In Sin Francisco, she was infected by Lust. For All Hell Break Loose, I do not really believe she turned evil because at the end, the Source ordered his subordinates to kill her after Tempus turned back time.

4. Every season there will be a loss of a regular actor in the cast.
Season 1 - Andy (T.W King) 
Season 2 - Dan  (Greg Vaughan)
Season 3 - Prue (Shannen Doherty)

5. When warlocks and demons attack, the things broken usually are the coffee table, the couch, the windows and the clock. I remember Prue being really furious about replacing furniture.

6. All three sisters fell in love with demons before:
Phoebe-Cole Turner, Piper-Jeremy Burns, Prue- under influence of the spell, she was married to a warlock (Bride & Gloom) and Bane Jessup.

7.  All 3 sisters fell in love with people they're not supposed to fall for:
Phoebe - Cupid, Piper - Leo, Prue - Bane Jessup.

8. Did you know: the taller Grimlock in All Halliwell's Eve, Shax in All Hell Breaks Loose and Belthazor (demonic form) are all played by the same actor? (Michael Bailey Smith)

9. Halliwell Factoid: Do you know where was Penny "Grams" Halliwell born? (Boston)

10. Halliwell Factoid: Do you know when did Patty Halliwell (the sisters' mother) died? (Feb 28, 1978. Prue was around 8, Piper was about 6 and Phoebe was 2.)