$5 off $19 Ka-Me Crackers KAMECRK5
$5 off $25 DeLallo DELALLO6
$5 off $29 SeaBear SEABER59
$5 off $40 Mom Made Meals MOMMADE4
$5 off $40 Mom Made Munchies MOMMADE5
$7 off two Cornuts and Kraft Mac & Cheese Crackers CORNYMAC
$10 off $29 Lipton Tea, Soups, and Knorr-Lipton Sides LIPTKNOR
$10 off $29 Dilmah, The Tao of Tea, and more SUMMBEVG
$10 off $29 Nong Shim NONGSHIM6
$10 off $29 J&D’s Bacon Salt BCNSLT59
$10 off $39 Honest Foods BARSJUN9
$10 off $39 Jolly Time JOLLYT15
$15 off $39 Stacey’s Chips PITAMDNS
$15 off $49 Kasilof Fish KASL3434
$15 off $50 Mom Made Baby Foods MOMMADE3
$20 off $49 Tasty Baby TASTY666
$20 off $59 Jack’s Harvest JACKHAR2
10% off $49 Vitalicious VITAL999
35% off $49 Happy Family Foods HAPPY666
20% off $59 Conte Pasta CONTE224
Buy 3 Get 1 Free Marques De Grinon PASTA333
Buy 2 Get 1 Free Happy Baby Foods HAPPY555
10% off three Sable and Rosenfeld SABLE444
10% off Paldo and Teumsae NOODLE69
10% (25%) off Eat Natural Bars EATNAT44
10% (25%) off Pop Secret POPSEC44
10% (25%) off Today’s Farm JUSTUS25
10% (25%) off Taylors of Harrogate TAYLORT2
15% off d’Marie TUSCAN69
15% off Italian Products TAZZAD69
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15% off Pretzel Pete Gift Box PRETZEL5
15% off Peas of Mind PEAS9999
15% off Callison’s SKEWER55
15% (30%) off Torani TORAN445
15% (30%) off GOJILANIA Goji Juice GOJIJUIC
15% (30%) off Mountain Sun Juice MOUNT323
15% (30%) off Breadshop’s BREADSH5
15% (30%) off Baxter’s Soups BAXT3333
15% (30%) off Terra Chips TERR9959
15% (30%) off Earth’s Best BESTEAR4
15% (30%) off Coombs Family Farms MAPLES35
15% (30%) off Baby Mum Mum BABYM676
15% (30%) off Savory Creations SAVORY55
20% off Ito En TTO54566
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20% off AriZona Iced Tea ARIZONA2
20% off Blue Cow Drink BLUECOW2
20% off Talbott Tea TALBOT59
20% off Highland Tea Company HIGHLAN5
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20% off Pasta Express PASTA669
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20% off RAB Foods MANISC59
20% off Petite Palate PETITE33
20% off Miss Leone’s Olives MARTINI6
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25% off Revolution Tea REVTEA33
25% off PastaCheese PASTA444
25% off Sea’s Gift SEAWED69
25% off Nestle 25NESTLE
25% off Cafe D’Amore DAMORECA
30% off Anteadote RTDTEA33
30% off Fox River Rice FOXRIC30
30% off Wrigley’s WRIGDEAL
30% off Sophia’s Gourmet SOPHIA99
20% (35%) off Tang ASTROTNG
20% (35%) off Country Time Lemonade REALCNTY
20% (35%) off Kool Aid KOOLDRNK
20% (35%) off Chamong Tea CHAMTEA3
20% (35%) off David Seeds SEEDSPTR
20% (35%) off Crystal Light CRYTLBEV
20% (35%) off Vita Coco COCON442
20% (35%) off Monarch Beverages MONARCHB
25% (40%) off Kashi KASHNTRL
25% (40%) off Special K SPCKDEAL
25% (40%) off Steaz STEAZ7I2
25% (40%) off Bear Naked NTRLGRNL
25% (40%) off Stretch Island STRCHBER
25% (40%) off Orville Redenbacher’s POPMSTER
25% (40%) off Slim Jim TSTYSTIC
25% (40%) off Blue Dog Bakery BLUEDOG4
30% (45%) off Bumble Bar BMBLE045
35% (50%) off Kitchens of India KITINDI5
35% (50%) off Corazonas Chips CHPHEAR5
45% off Panda Cremes PANDCRE5
50% off Silver Palate Oatmeal OATME333

For your question for how to find them, I always use below methods:

1. Go to grocery , healthy or electronics category pages of amazon.com
2. Sign up for amazon customers newsletter to receive promo codes.
3. Go to some coupon sites is a lazy solution. The sites like retailmenot.com, tophotdeal.com , mycoupons.com, are all good choices.

Wish this helps you.
References :