Precious Memories released several different K-on! sets of cards for their Japanese CCG. There were a staggering 1,053 cards made (there are a few more if you count tournament awards with stamps, etc)
Links below list the various sets, and there is a checklist with each set showing which cards were available.
Set 1 K-On! - 01-001 through 01-177: 163 Standard Cards, 88 Foil, 14 Promo, 7 Autograph (this was the very first Precious Memories set made!)
Set 2 K-On! Part 2 - 02-001 through 02-125: 122 Standard Cards, 70 Foil, 2 Promo, 5 Autograph
Set 3 K-On!! - 03-001 through 03-125: 122 Standard Cards, 70 Foil, 5 Promo, 5 Autograph
Set 4 K-On!! Part 2 - 04-001 through 04-127: 120 Standard Cards, 72 Foil, 4 Promo, 5 Autograph
Set 5 K-On! The Movie - 05-001 through 05-030: 30 Standard Cards, 30 Foil, 5 Autograph
Promo Cards P-001 through P-071: 72 (all standard) cards
Lawson Store Cards L-001 through L-023: 23 (all standard) cards, 2 Promo
Movie Cards M-001 through M-005: 5 (all foil) cards
Silver Foil Signed Cards: 1 random in each Starter Deck.
Gold Foil Signed Cards: Random Booster Pack Inserts rougly 1 per box.
Lottery Redemption Autographed Cards
Lottery Redemption Stickers (55 different?)
Starter Decks
Chara Sleeves
Precious Memories Official Site (Japanese, google translate does a decent job)
Japanese Precious Memories Wiki (abandoned, it seems)
Japanese Card Store with decent selection (you will need to use a buying service to get these outside of Japan though - this can get expensive very fast!) Note that for some cards out of stock they may have versions under the "scratched" section. I've bought a few of these and they look fine.
Japanese Card store that will ship directly to the US free, however the prices are jacked up quite a bit. I used this site in a pinch if there were cards that yuyu-tei.jp didn't have.