There are a surprising number of ways that you can effectively get permanent, low-effort, fairly large discounts on everyday spending—especially if you have the spending habits of a typical EAer (i.e., mostly necessities, relatively little eating out/entertainment, and strong credit). Here are some:
The US Bank Cash+ card lets you pick categories to get 5% off of (up to $2,000 per quarter). This notably includes charitable donations. Although credit card processing fees will eat some of this compared to donating via check/debit/direct transfer, you’ll still come out pretty far ahead. (Paypal charges 2.2% to nonprofits.)
For an effective 5% off of Amazon, use the Amazon for Effective Charities browser addons (instructions). 5% of each of your Amazon purchases will go to SCI.
The Sallie Mae Mastercard gives you 5% cash back on groceries, gas and bookstores, where bookstores include Amazon. (There are monthly caps on the cash-back amount of $250, 250 and 750 respectively.) Stacks with the previous for an effective 10% discount on Amazon.
PenFed offers a card that gives you 5 “points” per dollar spent on travel (including flights), although the “points” seem to be worth more like 0.8 cents. (Disclaimer: haven’t used this one yet; they lost my application or something.)
For other expenses the best discount you can get appears to be the Citi Double Cash card, which gives 2% back across the board.
There are some cards that offer rotating 5% cash back on different categories, which sometimes include eating out and potentially other expenses. I don’t usually use these because they require me to pay too much attention to the categories and I’m worried about them inducing me to spend money I otherwise wouldn’t.
My main expense that isn’t covered by any of these is, of course, rent, but credit cards are not so eager to give people discounts on that… on the other hand, I’m sure there are other potential discounts I’m missing.