This list will probably be biased towards Metal, since that's more my thing, and I'm just listing whatever's on my iTunes...
Bands/Artists:
Judas Priest, Jaguar, Jacula, Jex Thoth, Jotenheim, Jaz Panzer, Judas Iscariot, Jack Frost
Albums:
Fallen (Spiritus Mortis), Fallen Angel's Symphony (Ancient Ceremony), Far From the Sun (Amorphis)
Songs:
Jack (Iced Earth), Jack@ss In the Will of God (Eyehategod), Jack Daniel's and Pizza (Carnivore), Jack Tars (Saxon), Jack the Stripper (Black Sabbath), Jackhammer (Manilla Road), Jade (Flowing Tears), Jaded Entity (Cathedral), Jail House (Coven), Jailbait (Motorhead), Jailbait (Quartz), Jailbreak (Thin Lizzy, also covered by Six Feet Under), Jambord (Grand Magus), Jawbreaker (Judas Priest, also covered by Siebenburgen), Jaws of Satan (Sathanas), Jed's White Owl (Las Cruces), Jekyll & Hyde (Iced Earth), Jen (Count Raven), Jerhume Brunnen (Upwards of Endtime), Jester's Banquet (Chalice), Jesus' Blood (Nokturnal Mortum), Jesus Built My Hotrod (Ministry), Jesus Hitler (Carnivore), Jesus Saves (Slayer), Jesus' Tod (Burzum), Jewel of Atlanteans (Graveland), Jewel Throne (Celtic Frost), Jigolo Har Megiddo (Ghost BC), Jihad (Slayer), Join the Legion (Cirith Ungol), Jonah (King Diamond)...
.... and I'm gonna stop there.
Jonas Brothers
Janitor
Some 5-letter words beginning with 'j' are:jabotjauntjazzyjeansjellyjennyjettyjeweljiffyjimmyjointjoistjokerjollyjoulejoustjowlyjudgejuicejuicyjulepjumbojumpyjunkyjuror
Besides the letter J itself, another letter that starts with J is junk mail.
Jackol
what is a household chore that starts with a j
Jeweller Judge Journeyman
Jonas Salk
Japan is an island that starts with J.
jokester, jubilant, jonasey
One Celebrity that's name starts with the letter "J" is Justin Timberlake.
Jitterbug is a dance native to the United States. It starts with the letter j.