For the Adobe breach specifically, you might try the site set up by Last Pass, which checks your email against the breached data: https://lastpass.com/adobe/
The added feature is that, if your email is in the list, Last Pass will share with you how many others had your same password -- and the list of all password hints associated with that password. If more than a handful of others used the same password, that should jog your memory about which you used.
P.S. I'm not associated with Last Pass and actually use a different product. But I found this site very helpful.