Don't laugh - because I never thought I'd join AARP, but I just did, and in the first month I've received discounts on things I already pay for monthly anyway: my phone bill and audible subscription. They are also sending me a free utility bag which I probably don't need.
I joined for $12 a YEAR, (but I think that was a promo - it's usually $16)
I thought you had to be 50 but I just saw this on wikipedia: "There are no longer any age restrictions for membership.[17]"
I know they have other discounts on travel and other things - but I haven't explored any of it yet.