I have posted here before about Ibotta, an app that gives you cash back on groceries and such. Would you believe that I have saved $121 in August alone? To date - going back to March of this year - I've done $331.66, and have cashed out $300 of it to my bank account.
I mentioned before that there are other apps and such out there; while none of them hold a candle to Ibotta (in my book, anyway), there are several that are useful and do add up. If you put back, say, $20-$40 per month, leave it in an account, and withdraw it once it's enough to feel... isn't that worth taking a few seconds to scan your receipts or whatnot?
At any rate, I did a full writeup on the subject, covering eight different cash back apps. I hope that it's helpful to you!